I have an all original 1978 Pace Car (7,500 miles) L-82 with Automatic and AC that I need to replace the belts on and am trying to find a resource to verify the production date as Quanta Belts, the manufacture of GM replacement parts has a feature that specfies to input a production quarter. The sticker on the drivers door jamb indicates 4/78. Would this be the actual production date or just shipping date as the dealer documentation I have indicates a 4/6/78 ship date from GM and the Delivery Document from the truck line indicates a delivery of 4/12/78. 

4-78 would be the approximate build date. I would think your production date would be in the 3rd quarter, as far as belts, but the belts could have been manufactured several months before the car was actually built. In judging, we would consider any date before build date as correct.

btw...if you look on the trim tag, located on the hinge pillar forward of the door, you'll find the build date, as a code. Yours would be an "H" with a number after it. "H" = April, and the number would be the day in April the tag was affixed to the car. It may have been a couple of more days before the car was actually finished, but the trim tag date is what we all know as the "build date".



Here's a trim tag....