your Fiero swap options
Both have been done as you know. Of the guys I know with swaps I can tell you this. Northstars have been put in and pulled out due to problems on more than 2 occasions.
SBC's once done are normally rock solid, but more expensive to swap in due to all the bits and pieces required.
The fastest, bar none, is PBJ's 10 second 3800 turbo'd GT. He also had the fastest 4.9 turbo'd.
I am doing a 4.9 carb'd because I want some power and simplicity. It won't be the fastest, but it will still go well, and will be trouble free.
Hope this helps.