Beginning sometime in '68 Pontiac began stamping the last eight digits of the vehicle identification number (VIN) on the engine block. As you can see in the diagram at right, the number is behind the lower radiator hose next to the timing chain cover on the front passenger side of the block.|
Because of its position, the only way to see this number with the engine in the car is from underneath.
This view shows the positioning of the engine production number (which does not match the VIN) and the block code. This block code is 2 characters on most V8s and identifies the engine/transmission combination.
Again, this is a view of the front passenger side of the block with the heater and lower radiator hoses in the foreground. The numbers are just below the cylinder deck.
Here is a typical data plate. These plates are found on the firewall or on the top of the cowl on the driver's side of the engine compartment. Although each year is different (and some years had multiple data plate designs), the information is usually very similar.
"ST" stands for style. The model year is self explanatory. Immediately following the model year is the five digit style number which in most years identifies the exact car. This style number usually matches the first five digits of the VIN (Norwood Firebirds don't always).
Where the diagram shows the assembly plant this code does not seem to be the same as that identified in the VIN, so I usually ignore it. Unit number is the body serial number.
"TR" stands for trim. This number is found in most factory literature and will identify the trim level and color.
Time built code is a three digit code indicating the month and week the car was built. The first two digits are for the month (01-January, 02-February, ... 12-December). The third digit or character is the week (A-first week, B-second, etc.).
The numbers next to the "PAINT" indicate upper and lower exterior colors. If the car is a solid color then both numbers will be the same. On my Judge they are 72 72 for Carousel Red. If the car has a vinyl top, is a convertible, or is two-tone, one number will indicate the top color.
Most data plates have at least this information. Some will have much more, although the additional numbers may not have any decipherable meaning.