80 GP 3.8 to Pontiac 400 conversion
 

Have someone I work with has a 1980 GP with a 3.8 and auto and is wanting to put in a Pontiac 400. Anyone have any experience with this conversion, that can pass on some info what will be needed to complete it. He just bought a 400, but not sure yet what year it might be. Thanks

Get both sets of mounts from a 301 and as long as the 400 is a 70 up and it's a bolt in. I would upgrade to a Turbo 350 transmission as you don't have to change the driveshaft.
I did this conversion on my 85 Grand Prix.

The only other minor thing I can think of not already covered is Battery placement, the Buick and Chevy powered G-Bodies mount the battery on the passenger side, as the Pontiac V8 has the starter on the other side the battery is usually mounted on the drivers Side. And Fuel Line size, the V6 Fuel line is usually a smaller Tube than the V8 Fuel line.

Appreciate the feedback, I will pass it on. I gave him some miscellaneous parts he will need, as well as he got on a G body forum, as was able to have contact with a couple of members there, and will help him with some of the parts I did not have for him. He was not a Pontiac guy to start, but I think he is coming around. I applaud he is going the Pontiac motor route in instead putting a chevy in it.