[drptop70ss]

I havent done it, but I have done some other strange swaps. If you have a complete buick engine with all the related brackets, pullies, and a set of matching engine and frame mounts it should not be a big deal. Your pontiac trans will bolt up to the buick ok. To do it I would not bolt the frame mounts into the pontiac yet. Bolt them to the engine mounts and have the mounts bolted to the engine. Set the engine in the car bolted to the trans. With the car level side to side level the engine side to side. Check the frame to see if there are holes for the mounts, if not mark where you need to drill holes. Then pull the engine back out, mount the frame brackets, and drop the engine in. You will obvously need buick headers (skylark?) headers, and hopefully they will fit the grand am. I have been told they are expensive. There will be other small stuff to deal with but its not a major deal. Myself I wouldnt do it, there are plenty of pontiac engines out there, I recently picked up a complete bonneville with a 400 for $200. I would hold out for a pontiac engine, especially for resale value IMO.

EDIT To swap in a chevy would be basically the same as putting the buick in, but you would need a chevy transmission if you dont have a universal case. The parts needed may be cheaper. You may need to swap out the radiator.