Donald Farr
Former Editor, Mustang Monthly
June 1, 2009
Photos By: The Mustang Monthly Archives

"Matching numbers." We hear it all the time. It's tossed out proudly by car owners at shows. We see it used as a selling point for Mustangs for sale in classified and website advertisements. Even Speed TV commentators describe high-dollar Mustang muscle cars as "numbers matching" during televised, high-profile collector car auctions.

But what does it mean for '65-'73 Mustangs, and does it really have an affect on a car's desirability, collectability, and value?

The metal door data plate on '65-'69 models provides the most important numbers on a Mustang, including stampings for the VIN and codes for the engine, body style, interior trim, exterior color, build date, sales district, transmission, and rearend. Experts can spot whether or not a data plate has been replaced by the rivets.

According to Wikipedia, "numbers matching" comes from the collector car market to describe "the authenticity of collectible or investment quality cars, generally meaning that a particular car still has its major components or has major components that match what the car had when it was new." Major components are listed as the frame, engine, transmission, and rearend, which, in some cases, have the car's Vehicle Identification Number (VIN) stamped in them. To concours judges and collectors, especially those who deal with desirable Mustangs like Shelbys and Bosses, the meaning can go much deeper, right down to casting numbers and date codes on individual parts.

"Matching numbers can even get into how everything matches the build sheet and buck tag," says Ed Meyer, a noted Mustang judge, restorer, and expert on factory originality. "It's from bumper to bumper- even the bumpers are dated. The taillight buckets on '69s have a code for when they were assembled. Wiring harnesses have ID tags. There were tags on the seats with a date code; you can't see them unless you take the springs out. They had to have all that stuff in case there was a problem so they could trace it down."

In 1970, the metal door tag was replaced by a Mylar vehicle certification label, which includes the same basic information as earlier metal tags. Unfortunately, the typed lettering on these labels is prone to fading, making the codes difficult to read. In many cases, the labels have been painted over during repaints.

Corvette enthusiasts were likely the first to place such importance on matching numbers. When Corvette owners and restorers began taking cars back to original condition, they used the various ID and date-code stampings to determine if the car and its parts were original. As other vehicles reached collectible status, the matching numbers game spilled over into the Thunderbird, Mustang, and collectible musclecar hobbies.

What Does It Mean?
In its most basic form, a matching numbers Mustang has a metal door data plate ('65-'69) or Mylar vehicle certification label ('70-'73) with a VIN that matches the VIN stamped into the inner fender apron, as seen with the hood open and located in a fender cut-out on the driver's side. Because the VIN includes the engine code, you can also take it to mean that the engine must be the correct type for the car. For example, a '67 Mustang with a later 351 Windsor engine would not be considered numbers matching. The data plate (sometimes called warranty plate) also includes codes for the body style, exterior color, interior trim, scheduled build date, transmission, and rearend axle ratio, so those items are also considered in the matching numbers identification. On '68-'73 Mustangs, the VIN on the data plate and inner fender should match the VIN on the windshield VIN tag, which was mandated by the federal government beginning with '68 models.

Matching numbers have become extremely important to collectible high-performance Mustangs like Shelbys, Bosses, and Cobra Jets. You'll hear the term used often at collector car auctions.

Over the course of four decades, most of today's surviving '65-'73 Mustangs have experienced any number of misfortunes. Many don't have their original engine due to service replacement or a performance swap. Damaged original doors have been replaced with good doors (and data plates) from other Mustangs. Cars with heavy front-end damage have been "clipped," meaning their front-end assemblies (with the stamped VIN) have been replaced with front-ends from wrecking yard donors. In the last two examples, the door data plate won't match the stamped inner fender VIN. Sometimes, data plates are missing entirely. On the later '70-'73 Mustangs, Mylar certification labels are often faded beyond readability or painted over. So there are any number of reasons why a Mustang may not be numbers matching today.

Every vintage Mustang's VIN is stamped in the driver's side inner fender apron, which should match the VIN on the door data plate or certification label. We've seen plenty of variations over the years. Some are not centered in the outer fender's cut-out area; others may by double-stamped almost beyond readability.

With the recent publishing of Kevin Marti's The Mustang and Cougar Tagbook, the previously mysterious buck (or build) tag, as found on many first-generation Mustangs, has taken on new meaning when it comes to matching numbers. According to Marti, these metal tags were attached to the front subframe so the Body and Paint line at the assembly plant could build the vehicle to order. Because some options required the drilling or punching of holes for installation, they were identified by codes stamped into the buck tag. For example, racing mirrors on '69 Mustangs required holes in the doors, so they were identified by either "RAC" (Dearborn), "RM" (Metuchen), or "3" (San Jose). As you can see, the codes varied by assembly plant. Also adding to the confusion is the fact that not all early Mustangs came with buck tags. For '65-'66, only Metuchen-built Mustangs have them. The other assembly plants began using them, affixing them to different spots under the hood, in late 1967 (Dearborn) and late 1969 (San Jose).

Thanks to the information in Marti's book, new importance is placed on the buck tag because the stamped VIN offers yet another matching number and the codes provide proof of many important factory options, like the GT Equipment Group, air-conditioning, and upgraded stereo radios.

Shelbys received their own VIN plate over the Ford inner fender VIN stamping. For matching numbers, a Shelby VIN must match the Ford VIN underneath, which can be verified by the records maintained by the Shelby American Automobile Club.

You can take matching numbers to the next level by matching the engine to the car. This can be difficult for '65-'67 Mustangs because, with the exception of the 289 Hi-Po, the car's VIN was not stamped into the block. It's assumed that the Hi-Po was stamped either for warranty reasons or for identity purposes because those engines were more likely to be stolen.

However, beginning in 1968, federal law mandated the stamping of VINs, or partial VINs in some instances, on engines and transmissions. On Fords, the VIN is typically found on a pad at the rear of the block, between the intake manifold and transmission bellhousing. If the stamping matches the VIN on the data plate and inner fender, then it's the original block to the car, a plus for talking points and value. However, as Mustang restorer and MCA judge Bob Perkins points out, just because an engine VIN is missing or unreadable doesn't mean the engine is not original to the car. "I've had untouched Boss 302s that didn't have VINs stamped in the motor," he tells us. "And I've had them where they're partially stamped. I've got a Boss 302 where you can read the 0 and the F, but most of the consecutive numbers are so far off the edge you can't see them."

In 1968, the federal government mandated the placement of VIN tags riveted to the lower instrument panel at the bottom the windshield to make it easier for law enforcement officers to spot stolen cars. These tags are found on the passenger side of '68 Mustangs; they were moved to the driver's side for '69 and later. On '68-'73 Mustangs, this VIN must match the VINs on the door data plate and inner fender.

Engines also came with an identification tag that provided the engine code, displacement, date of manufacture, and other pertinent information. Over the years, most tags have been discarded during engine rebuilds so it's rare to find an engine with its original tag still intact.

Other major components, like transmissions, rearends, carburetors, power steering pumps, and steering boxes were also equipped with identification tags, although the presence of the correct tag doesn't always mean that the component is original to the car. In some cases, the tag may have been transferred to a replacement part. Marti's book includes a decoding section for the tag codes.

Casting, or engineering, numbers are another way of identifying parts. Nearly every part, from the engine block to the taillight lens, has a Ford casting number. While the correct casting number on a part doesn't always prove that the part is original to the car, it does make it correct to the car.

Digging even deeper, most parts have date codes that can determine if the part could have originally been installed on the car. "If the date codes pre-date the car build within a good time frame, that's as good as you can get," says Meyers. "Sometimes it can be two to three weeks before the car was built. I've even seen three or four months. It just depends on where the stuff was stored and how they rotated inventory."

For years, Mustang owners pondered the meaning of this oddly shaped metal tag and its stampings. Found under the hood of many Mustangs, depending on model year and assembly plant, the body buck tag contains the car's VIN along with codes for options and colors, making it a useful tool for verifying a Mustang and its original equipment.

Bob Perkins puts a lot of stock into date codes but not necessarily the ones everyone thinks about. "I think the sheetmetal is important," Perkins says. "I don't think carburetors and other bolt-on items are as important because you can install a carburetor with the right numbers and date code, but it could be off another car and nobody would know the difference. For numbers matching, I want all the spot-welded panels to be original to the car. People worry about a date on a '69 Mustang's carburetor, but it'll have '65 floorpans. That's a way more serious problem than a wrong date code on a carburetor."

Date codes can be complicated because Ford's coding procedures were not consistent. Some parts are coded by year, month, and date, while others indicate month, date, place of manufacture, and shift. You can find additional information about date codes at www.hammar.dyndns.org/datecode.htm.

The best source for determining Mustang matching numbers is Kevin Marti's The Mustang and Cougar Tagbook for '65-'73 models. The book includes decoding information for data plates, engines, transmissions, carburetors, buck tags, and other identifying tags. It's available from many Mustang parts suppliers or directly from Marti Autoworks, www.martiauto.com.

Matching numbers even go beyond stampings, ID tags, and date codes on the actual vehicle to include factory documentation, like the Ownercard in the glove compartment, original bill of sale, window sticker, and build sheet. All include the VIN and other information, including dates, equipment, and options. Today, owners can also verify their cars with information from Kevin Marti's Ford production database. Available for '67-'73 Mustangs, these "Marti Reports," as they are known in the hobby, come from the Ford database and verify scheduled and actual build dates, options, colors, selling dealer, and other information.

Another form of verification is the original sales invoice, which includes the VIN, model, equipment, options, and pricing information. Ford typically trashed these invoices at a certain point in time, but former Ford employee Lois Eminger had the foresight to save many of them and offer them to owners. When Lois passed away last year, Marti acquired the invoices and added them to his services. Invoices are available for most '69-'73 Mustangs built at the Dearborn and Metuchen assembly plants.

Beginning in 1968, VINs were typically stamped into a pad on the back of engine blocks. Often hard to see when an engine is installed and many times difficult to read due to stamping irregularities, the number is very important to determining original blocks, especially for high-performance Mustangs. This '70 Boss 302's pad is blank, meaning more than likely it's a service replacement block.

To restorer and auctioneer Drew Alcazar, a factory build sheet is the ultimate documentation. Used by assembly line workers to complete cars with the right equipment, these sheets were often stuffed between seat springs, wrapped around wiring harnesses, or simply tossed under the back seat or carpet. Not all cars have them, and even when found many are faded or damaged beyond readability. Build sheets include codes for most of a Mustang's major components, from spindles and stabilizer bars to mufflers and tires. You can take matching numbers to the max by matching the codes on the build sheet to the components on the car.

For owners lucky enough to have their Mustang's build sheet, Drew offers this bit of advice: "Don't laminate a build sheet. That's the first alarm bell that goes off that someone is trying to do something fake. Ten years or so ago, people were doing it right and left because they were trying to preserve them. Never do anything other than put it in a clear acetate sleeve."

Does It Matter?
To perhaps 90 percent of vintage Mustangs, matching numbers is a point of interest but not a concern when it comes to collectability and value. It's great to be able to point to the distributor and say it's original to the car, but if it's incorrect on a '66 GT hardtop or a '67 convertible, it's not going to hurt the value or appeal.

Casting (or engineering) numbers are found on most factory castings and can be used to link the part to a particular Mustang. The C80F-J casting number on this distributor indicates it was originally installed in a '69 Cobra Jet engine with the automatic transmission. The date code 8J9 is also visible-for September 9, 1968.

"I believe there are three levels of Mustangs," says Alcazar. "You have hobbiest cars, about $25,000 and under. This is a '66 coupe with a 289 and a bench-seat and the owner does the club thing and cruises. The next step is enthusiast cars, which have a value range of $50,000-150,000. These are the 428 CJ Mach 1s, as an example. There's nothing collectible about these cars. They made thousands of them. Where the conversation has genuine merit is when you talk about the third level-collectible American muscle cars. That's when you're in that quarter million dollar range. You're talking '66 Shelby GT350 convertibles and R-models. With those cars, you're in a whole different realm of discussion when it comes to numbers matching."

Perkins sees it from another point of view: "I think it matters a lot on cars where people are concours oriented or it's something special like an original paint car. On a Boss in particular, people are numbers conscious because everybody knows that the engine and tranny were supposed to have the VIN number stamped in them."

The Parts Identifier and Interchange Guides from Warner Robert Publications are excellent resources for decoding Ford casting numbers. Often used by collectors, car-show judges, and restorers for determining correct parts, the guides are available for '65-'68 Mustangs and Shelbys, '69-'73 Mustangs and Shelbys, and '60-'73 Ford performance cars. You can order through the website at www.warnerrobert.com.

But to Perkins, the numbers aren't as important as his own knowledge of what's original. "I can look at the overspray on the bellhousing and things like that to determine that an engine has never had a new block put in it. You can take kind of an educated guess to say that an engine has never been out of the car."

"If you care about numbers matching, it's probably because you're planning to enter concours at an MCA show," says Kevin Marti. "So we're talking a very small percentage. Most people just want a Mustang; they don't care so much about why it's the way it is."

When we talked with Meyers, he was in Arizona confirming the originality of a Boss 429. "It means more to Mopar and Chevy people than Ford people because you can see the numbers on their cars," he told us. "I just spent 20 minutes trying to figure out if a Boss 429 had the right transmission. On Fords, it's hard to see the numbers in the cast-iron, four-speed or automatic. On a Chrysler Six-Pack or Hemi engine, the date code is on the left side of the block in letters that are an inch tall. There's no hiding it. But on Fords, it's a little-bitty thing in the sand casting. You can't make out half the numbers."

There's also the matter of fake or counterfeit data plates or identification tags. Just because a Mustang has a data plate that matches the inner fender VIN and equipment doesn't mean the car was born that way. Reproduction data plates and other tags have been available for years, with some owners changing codes to match the car and its current color, options, and equipment. Experts like Perkins and Meyers can spot reproduction data plates and tags by the stamping method and even by the rivets or screws used to attach them.

The C5AE-6015E casting number on this 289 Hi-Po block is correct for a '65 K-code Mustang. The 5J20 date codes indicates that the block was cast on September 20, 1965, so it would not be correct for a car built before that date.

The Mustang Club of America, which is known for its concours judging standards, accepts reproduction data plates. "As long as the car is restored to the reproduction door tag, we couldn't care less if it was originally a GT, or a red or black car, or Pony interior or standard interior," says Perkins, who serves as a technical advisor to the MCA. "In defense of the MCA, there's no Marti Reports for the early cars. On '67 and later Thoroughbred class cars, I think owners need to show a Marti Report. If you've changed the exterior or interior color, you're going to take a hit for it."

As the president of the Russo and Steele Collector Automobile Auctions, Alcazar has seen the more serious side of defining matching numbers. "My clients have tied their tails together numerous times," he told us. "You can forget the ambiguity of what numbers matching means from a restoration or judging perspective when it comes down to a couple of guys who spent a ton of money on a car and who now disagree with each other and have hired attorneys. All the rest is a picnic."

Sheetmetal date codes didn't include the year. Instead, the code provided the month and day of manufacture, the plant, and the shift. This "7 15 C3" stamping on a '65 Mustang front fender reveals that it was made on July 15 at the Cleveland stamping plant during the third shift.

So is there a legal definition of matching numbers? "Not necessarily," Alcazar says. "But you realize how ambiguous some of the descriptions are by getting placed in the middle of what is essentially the buyer's discovery duties and the seller's disclosure. It's amazing when people spend hundreds of thousands of dollars in attorney fees trying to figure out the definition of that ambiguity."

Matching numbers cars are collectible because they are much rarer than non-number matching cars. They also represent a look back in history, which is what ties matching numbers to collector car values. As years go by, matching numbers Mustangs are going to become rarer and even more special. "As parts wear out or vehicles are damaged, fewer Mustangs will be numbers matching in the future," says Marti. "As this ever-shrinking survivor group moves more into the realm of historical icons, I hope owners will do their part to conserve, protect, and preserve the herd."

Boiled down, matching numbers only matter if you're serious about concours or you're talking serious bucks for a collector-type Mustang. If you've got a regular '67 hardtop or '73 convertible and you can point to correct date codes and show off the original bill of sale, that's great from an interest standpoint. But it likely won't get you thousands of dollars extra when you sell it.

Major components like steering boxes were identified by stampings on tags. Because '65-'66 GT Mustangs came with a quicker steering ratio, they need to have the quick-ratio steering box, as the HCC-AX here indicates. The "5K25B" date code breaks down to October 25, 1965, second shift.

Still, Ed Meyer isn't so sure about matching numbers. "A lot of people stay away from the subject because there are so many variations between years, makes, and models. You're probably opening up a can of worms."

Four Legs Of The Stool
As president of Russo and Steele Collector Automobile Auction, Drew Alcazar has his own unique spin on matching number Mustangs. He sees it as four distinct levels, or "legs of the stool."

Numbers Matching: "The lowest level is numbers matching. That means someone assembled a group of parts that in theory would have been made in a window of manufacturing opportunity that would say, 'Yes, these parts were born about the same time as the car.' If you have a block that's dated in the third quarter of '68 in a car that was made the first quarter of '68, you've got a problem because the car was born before the engine. It's not easy but with enough tenacity, wherewithal, and dedication, a guy can figure out a way to put together a block made within the quarter that his car was, a couple of heads that were cast a couple of weeks within the block's casting date, and a carburetor manufactured during the previous quarter or half year as the car. In theory, these parts were born at the same time or before the car. So numbers matching means you have parts that are correct for the car."

Original numbers matching: "This means the parts were installed on the car when it went down the assembly line. This is the engine that went into the engine bay, these are the heads that were bolted to the engine, this is the manifold and carburetor that was bolted on top of it. This is the sheetmetal that was destined to be a GT350 or shock towers that were formed and the body bucked to be a Boss 429. It's like being kind of pregnant-you either are or you ain't."

Most Ownercards have been lost or discarded over the years. They are very important to numbers matching collector cars.

Documented original numbers matching: "This is the holy grail. Now you have a car that was born with these parts, restored exactly the way it came down the assembly line, and you have documentation to prove it. Probably the loosest form of documentation would be notarized previous owner affidavits - letters from previous owners that say this car, when they bought it, was a four-speed car. The next step up is dealer paperwork, like copies of the dealer invoices when the car was originally sold. The kicker is, all of this stuff can be forged; I have seen some brutal forgeries out there. Then you get into factory documentation - warranty cards and the original body buck tag. Of course, there are people who can make these things seem absolutely genuine, so there's this red-flag, buyer beware thing saying that just because somebody has this stuff doesn't mean it's original or authentic. The next thing is the build sheet. A genuine build sheet has all of the numbers and codes so it's the ultimate documentation."

Intact and readable build sheets are one of the most important documentations for a collectible Mustang. If you can match the codes on the build sheet to the codes on a car's individual components, you've found the holy grail.

Third party authentication: "This is the fourth leg of the stool. I call it the sprinkling of holy water. You now have people like Kevin Marti who can do the numbers analysis and tell you when a Mustang was built. You have the Shelby American Automobile Club to document Shelbys. I have a lot of respect for these third party verifiers. When you think about it, they have placed themselves in harms way to try to assist the hobby for a greater good."

Is Your Mustang "Numbers Matching?"
Stamped Numbers

  • VIN on data plate matches VIN stamped into inner fender and windshield tag ('68-'73)
  • Engine, transmission, rearend, color, and interior correct per VIN and codes on data plate
  • Buck tag (if equipped) VIN matches;option codes correct

Engine

  • Engine correct per block casting number and date code
  • Engine correct per VIN stamping (Hi-Po and '68 and later)
  • Correct engine tag
  • Heads correct per casting number
  • Intake manifold correct per casting number and date code
  • Distributor correct per casting number and date code

Kevin Marti's Ford database has made "Marti Reports" an essential link in the matching numbers chain.

Drivetrain

  • Transmission correct per data plate code and casting number
  • Rearend correct for the vehicle

Tags

  • Correct tags on engine, transmission, and rearend
  • Correct tags on carburetor, steering box, radiator, etc.

Date codes

  • Dates on all components pre-date the build of the car by a few days to several months

Paperwork

  • Build sheet (should match VIN and equipment)
  • Owner/Warranty Card
  • Original sales invoice
  • Original bill of sale
  • Marti Report ('67-'73)