Lots of good info...
http://www.gafiero.org/bbs/index.php?topic=873.0If the engine you're buying is one of the latest ones, I think it's worth 110-120 HP (I forget what the Wikipedia page said.)
But that's supposed to be attributable to the higher 5500 RPM redline. You might be able to squeeze a few more out of it with a cam swap or maybe a bit more flow through the intake. (All speculation on my part.) In any event, the Fiero bottom end is reputed to only be good for ~150(?) or so before reliability starts to be compromised, although the 87 and later cranks are supposed to be stronger than the earlier cranks, due to the DIS trigger wheel, among other things.
Keep in mind that this information is all speculation on my part, and is worth exactly what you paid for it.

All kidding aside, Pat / TopNotch is probably the club expert on these engines.