Well rule of thumb, even if you are rebuilding an engine. You want to find a good clean one that hopefully does not smoke. A smoking engine is often a sign of neglect. ie: overheated, infrequen oil changes ect.
This may lead to: warped cracked heads, skored cylinders (you can only bore so much), hairline fractures in the crank. Those are all big money items.
Best thing to do, call insurance companies and get one that was wrecked.
As for the flywheel: I'm not 100% sure alle 3.4L were internalyl balanced.. I would match the fiero flywhell to the weight balance of the 3.4L flex plate or flywheel.
For a turbo 3.4L, use teh same cluch as we will in the 3800sc. I think it Bulley or something.. I'll get more info.
Gary was right, use the release bearing from the donor tranny. (284 Getrag). I'd go with a SLIGHTLY stiffer pressure plate. DO NOT go overboard on the pressure plate. The hydrolic system on the Fiero is weak to say the least. and the stiffer pressure plate makes normal driving a chore.
Eric