Confirming a Matching Numbers Vehicle
What to check to authenticate your GM musclecar
For the purist musclecar collector or restorer, having a "matching numbers" vehicle is extremely important. A musclecar that still has all its original parts is more valuable than one that has been restored with reproduction parts. Originality is considered the basis for value, particularly when it comes to low production number vehicles such as the 1969 Trans Am or 1970 Buick GSX, both of which had less than 700 total units manufactured.
A Match Means Money
Always use accurate reference materials when researching your favorite car. Most restoration suppliers have books containing all the important information you will need to confirm the "numbers" for any make and model musclecar. If correctly coded parts are important to you, always do your homework before buying a vehicle so you don't purchase a clone or well-disguised counterfeit. Here in our Image Gallery we will examine the number and letter codes, and their locations, for most of the 1964 to '72 GM "A" body musclecars, which include Chevrolet, Buick, Oldsmobile and Pontiac. There are some variations within each manufacturer, but with the right reference material you will have no trouble verifying your car, hopefully before the purchase. Our examples are from a "matching numbers" 1970 Pontiac GTO.
A letter code is generally used to identify the horsepower and application of the block. In this case, we see the engine block manufacturing sequence number and the YS code denoting a Pontiac GTO 350-hp, 400-cid engine. Some GM manufacturers used 3-letter codes as well.
Every carburetor installed at the factory has an identification number and year stamped on it. Here we see a Rochester Q-Jet ID number, with date of manufacture. This car was built in late October 1969, so all the dates should precede that by a few weeks.
When GM was manufacturing the cast engine parts like intake and heads, each piece was date-coded as we see here. This code translates to "K" for October (the letter "I" was not used as it could be confused with the number 1), 12 for the 12th day and 9 for the year 1969.
This casting date is hard to read because the casting itself is rough and the date is not sharply defined. It reads K079, which fits with the rest of the correct date codes thus far. The opposite head was cast K089, or one day later.
Both automatic and manual transmissions have ID information. This plate decodes as 70 for the model year; PY is M40 standard 3-speed Hydramatic (or Turbo 400), with the manufacturing sequence number to the right.
The rear axle ratio code is normally stamped on either side of the axle tube. Here we see "XF" which translates as 3.23 Safe-T-Track (or Posi) rear end. It's one way to identify the rear gears without the benefit of an original factory build sheet.
The date of manufacture for the rear end and the casting number is usually on the gear housing or "pumpkin." Ours coincides with all the rest of our numbers showing K069. The 9799100 casting number should be the same on all 1970 Pontiac 10-bolt rear ends.
Every musclecar has a data plate attached, usually under the hood, with important information. This plate gives codes for body style, date of manufacture, interior color, assembly plant, exterior color and accessories ordered.
Even things like the cooling fan have date codes and part numbers. This original fan has codes on each blade. Ours is J69 or the month before the car was manufactured. The 9796134 stamping is the Pontiac part number.
Stamped inside the air cleaner base is the date of manufacture 8-18-69. As you can see, almost everything has some kind of code or number for proper identification.
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