On to documenting your car for the registry…

To begin with, the primary goal of this documentation is to guide you through properly registering your 1968 Z/28 for the 1968 Z/28 National Registry. This guide is not an all inclusive documentation source. Secondarily, I would hope it helps you to gain a greater level of appreciation for your car as you gain knowledge through the registry process.

The VIN number:

The VIN is a 13-character plate that is located on the driver side instrument (dash) panel visible through the windshield. This is the unique identifier for each car and will be the unique key in the registry database. A 1968 Z/28 VIN will always begin with these first 6 characters - 124378

The Trim Plate:

The Trim Plate is located on the driver side firewall. The Trim plate will give you the interior color, exterior color, and build date (basis for documenting proper date codes on all drive train componentry). As mentioned before, there is no proper way to verify the car is a Z/28 from the Trim Plate (unlike the 1967 and 1969 Z/28s).

Supporting Car Documentation:

There are two sources of documentation that verifies that your car is a 1968 Z/28. The first source is the 302 engine itself which we discuss in a little more detail in the Engine section. The other source is the various supporting documents the original owner received when he purchased the car from the GM dealership. Unfortunately, after several decades, and usually several owners, these pieces of documentation get lost or destroyed. As mentioned, you can verify that a car is a Z/28 from the information gathered off the engine, but without any of the following supporting documents, the car options can not be tied directly with the car. Lack of supporting documents does not usually detract from the value of a car but does help to differentiate and make a car more attractive to collectors because they help to give the truest picture of the way the car was in its original form. It is quite common that most Z/28s were not heavily optioned since many were primarily purchased for racing purposes. A heavily optioned Z/28 is highly desirable and would be given a premium value if supporting documentation exists. This brings up the point that documentation is very important today because many of these options can be easily bought from specialty part dealers and added to the cars therefore making it difficult to distinguish an original optioned car from a car that was altered after the fact.

Protect-O-Plate (Warranty information card) - a small metal card that resembled a credit card. This card is fairly rare because it usually remained in some fashion with (or lost by) the original owner or taken away by dealers on trade-in (to protect the privacy of the original owner). This card gives the original owners name/address, Trim plate information, how the car was equipped, and all the pertinent drive train information.

Broadcast Sheet (Build Sheet) - This computer-generated piece of paper gave a complete account on how the car was manufactured on the assembly line. Build Sheets have been known to be place in just about any location on a car. Most are never found or destroyed over the years and are a very rare. [Find an example to display - see page 32 in Scott's book]

Dealer Invoice, Window Sticker, New Car Order Form, Decals (Posi-traction trunk lid decal, Tire Pressure Glovebox Decal, Ignition Timing Decal, etc) - These are all great sources of documentation that supports at various degrees what equipment a car originally came with.

Car Drive Train:

Engine - The engine is one of the most important sources for verifying that your car is an authentic 1968 Z/28. As mentioned previously, the 302 Z/28 motor is really the high point of these cars. It is arguably one of the hottest GM production small blocks made in the muscle car era. It is important to properly document this motor and is the most critical area of value to the car.

The engine can be verified by reviewing the two-part engine block identification code, which is located on the front of the engine block at the base of the passenger-side cylinder head. The first part (Engine Block Vehicle Code), a nine character code, will always begin with "18" followed by an "N" or "L" then the last 6 digits of the VIN. The second part (Engine Production Code) is a seven-character code that always begins with a "V" and ends with "MO".

Transmission - A 1968 Z/28 came with one of three 4 speed transmissions - the M21 close ratio Muncie 4 speed (which was standard) or the M22 heavy-duty Muncie 4 speed (close and wide ratio which were optional). For identification purposes, an M22 will have a drain plug at the bottom of the transmission case. An M21 has no drain plug (must be drained and filled from a plug on the driver-side of the case). An M20 wide-ratio transmission was also available but was seldom ordered. This is ironic due to the fact that the low torque 302 performed much better at the start with a lower 1st gear.

The Transmission can be documented by viewing the passenger-side of the transmission case. You will find a five-character code (Transmission Assembly Date Code) that will always begin with a "P8" then followed by an alphabetic character and two numeric characters. Directly underneath this code you should find a 9 character code (Transmission Vehicle Code) that will match the Engine Block Vehicle Code ("18" followed by an "N" or "L" then the last 6 digits of the VIN).

Rear Axle - The standard rear axle ratio for 1968 Z/28 was 3.73 contained within a 12-bolt rear axle housing. The Rear Axle Date Code for the axle housing is located on the center section of the Axle near the inspection cover. The first character of the code will be an "A" through "L" followed by "1" through "31". The last character will always be a "7" or "8". The Rear Axle Ratio Code will always begin with two Alphabetic character (translates into an axle ratio) then several spaces followed by 4 numeric characters (designating month and day). The next character is a "G" followed by a "1" or "2" (designates the shift when it was built). If it is a Posi-traction Rear Axle, a one character alphabetic code ("D" or "E" or "W") is located below the Rear Axle Ratio Code.