The Barretta trans requires some converting (I think) to make it work in the Fiero.
Also remember that the lower 3.91 gear that I think you're looking for is only found on the quad-4 equipped cars not the regular V6's.
Rodney Dickman has done not only the Barretta
swap but the 3.91 gear swap into a regular Getrag as well. You might want to email him
since he knows a lot about this subject.
Here's his web-site:
www.execpc.com/~rodney1/ ------------------
Dave Gunsul
N.I.F.E. member
86 GT modified
85 SE daily driver