i used to have a 88 fiero with the 2.5L and the 5speed. had some konis and some other small odds and ends. loved the car. i want to get another one sometime.
4 banger… crap. the cyl bores are thin and weak and cant handle more than 180 reliably. the crank cant handle more than 5000r’s reliably for extended periods of time.
When I get another one, the last thing ill do to the car is put more weight in the back. i think the smartest swap would be an aluminum ecotec. id keep the ecotec trans and make custom mounts, axles, and cabling to make it work. little bottom end build and a turbo an it would be a fun little beast. 
Brian