Thread: Block VIN and other codes and numbers - 1974 or 1975.

Thats an early (cast on January 25th) 1975 4-barrel 400 with automatic trans. Last of the good ones. The last six digits of your block code are sequential and would match it to a car if it had the same last six. Original head castings could provide clues but as far as what kind of car it came in, I would guess Firebird. Can't nail that down without records but its no matter if you're not trying to prove it belongs to a certain body. All the answers are at the top page of a google search, as you might have found.

http://www.pontiacpower.net/castnum01.html

Beginning in mid 1975, blocks were cast with less material in a couple areas and they changed the crankshaft flange. This limits performance potential somewhat. I have a used up 988 block and also one of the later ones and you can tell side by side. Block casting changes applied to 455s also.

That I do not know. I do know Atlanta made lots of Grand Prixs in lots of years. My 72 was built there. I had a 75 GP with a 400 4 barrel automatic but it was in the early 90s and don't remember which plant.