1985 Buick Riviera Engine and Tran combinations.
 

Hello everyone, I own a white Buick Riviera and would like to put a new motor and trans in. I was hoping to put in a chevy 350 long block in but I am unsure of the fit. What is the best combination for my ride?

You are playing with a vehicle that is computer controlled.
The smart thing to do is stick with the way it was designed unless you are going to completely eliminate all the circuitry and controls and go back to pre 81 years.
It is either all or none, no half way.