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

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,

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.