I used a 3.1 out of a Z24 Cavalier. I used a DS1 turbo, so I used the 2.8 heads so I could use the OEM intake. I cant remember oil pan. Why not just keep the original 3.1 heads ? I believe in OEM clutches unless you have large hp engine, you will usually have a lot less hastles. OEM Fiero clutches have enough issues by themself
without throwing more unexpected ones in the fire. Mine was also blueprinted and put out great hp numbers so it had plenty of ' go ' I ran it richer than normal, so only got about 16-17 mpg (because of turbo). I never had any problems in over 100K.