Need input from "later"/post 80 GP owners

[shotgun]

I am looking at a 84 GP.

I have always had "early" ones (78-79-80).

How are the post '80 cars for interchangeably?

Did they have aluminum bumper supports? Front ? Rear?

How about interior trim, what years are interchange?

 

[dougfather]

Here are a few things I know of:

-sheet metal is different for 78-80 vs 81-87
-interior is mostly interchangable thoughout the years. The wiper switch was reloctated form the dash to steering coulmn in '82, so the bezel and stalk will be different
-not sure about aluminum
-81 was the last of the Pontiac engines in these cars.
-83 was the start of the Chevy 305 (option). Most I ever encounter have the Buick 231 V6
-chasis stuff stayed mostly the same (78 had some differences).
-84 and up has the frame mounts for the 200-4r transmission crossmember