I just finished off doing the axle swap game.
Just thought I'd make a simple and clear post to try and clarify what worked for me (YMMV!!!), to clear up some of the confusion in other posts (that usually started with "what works?" and got 75 different methods).
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The Subject Swap:
'92 4.9 with 4t60E, using BubbaJoe mounts (so engine & trans moved ~1.5" to the right), '86 cradle.
RIGHT (psgr) side of Fiero:
Fenco CV5542
Fits "as is".
LEFT (driv) side of Fiero:
Fenco CV3012
Remove outer pot. Replace with any Fiero outer pot.
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Hope that clears things up for someone! 
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87/88 V6 5spd "FormulaGT" Turbo, 85 Bright red GT 4spd (with matching 1:18 diecast and 1:24 plastic models!), 86 SE (custom body in progress)
My pages:
http://www.fieroclub.com
http://www.fierohut.com
