I appreciate you setting me straight on this bolt pattern point. Having said that, I have cobbled a lot of things over the years but have never even thought of installing a trans with bolts missing. I want to put my adivce/comments in the context that they were given. When someone asks for advice I believe they should get the correct advice and not advice that is dangerous or just plain wrong. I believe bolting a Pontiac trans with four bolts to a 454 is just asking for trouble that's why I butted in with my rough comment. A Pontiac transmission was not designed to be bolted to a Chevy engine period. Of course, if you have the correct adapter plate you might get by.
Jim