It's more out of curiosity since it won't affect anything anymore, but in my 89 Brougham the 307 is replaced with a 74 Olds 350 with a non computer controlled carburetor and distributor and a th350 transmission. that's a lot of sensors missing. for some reason though, when I put it in diagnostic mode, I just get 12 over and over, but none of the other codes associated with most of the inputs missing.

 

The computer doesn't know the engine is running, would be my guess.