I had a Mustang in highschool that we rebuilt the 289 motor on. I had bought a stock 289 rebuild kit from TRW and rebuilt it in autoshop class. Car never sounded quite right and seemed to have power issues too. We took it apart and completely rebuilt it a second time. The shop teacher was stymied. One day in complete frustration I took it to a Ford specialist. Turns out they sent a 302 crank for a 289 set up. About a year later, I sold the engine and bought a used 289(money was very tight back then and I was in school away from home, riding a Honda 750! Never did get that engine to work right. Still not sure if there wasn't a problem with the heads! Get the parts list as suggested above, and better yet find out who built it. Taking it to a good chevy guy wouldn't hurt either. With a 454, you should be able to smoke the tires off of the fiero, just be careful, those cars were know to catch on fire in thier day, maybe that's why they called them fieros?