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