http://www.v8archie.com/
You can put pretty much any engine GM makes into the fiero. Some engines are a little more difficult to do, but the quad 4, 3.1, 3.4, and 3.8 supercharged engines are also common.
http://pisafierohq.com/ this is a pretty cool place also, it might give you some idea of the versatility of the fiero.