v6 upgrade possibble???

I have a chance to get a 85 GT but the body is rough. Are there any gotchas related to switching my 4cyl for the 6 from the GT? I would also be going to stick verses auto which I have now. My Fiero is an 84.

It would be easier to switch the body from your 84 to the 85. That's pretty much what you are going to end up doing....the frames are pretty much identical, the body is identical...minus the bumpers, but the swap from an automatic to a stick is not easy and requires almost all the interior to be removed because the wire harnesses are not the same. So as long as the frame on the 85 is in good shape, i'd rebuild it instead.

Also the 84 never had a V6 in its plan so the wiring is a PITA adding a V6 or any other engine to an 84. A panel swap would be the easiest route.

panel doesnt take long trust me...we had a 86 se with a bad engine a good body...and another 86 se with a good engine horrible body and steering....trust me body is the way to go...

Besides the already noted challenge of swapping and possibly modifying wiring harnesses, it's an absolute pain in the neck to get the clutch/brake pedal assembly out. If by "body" you mean the plastic panels, using the 84 parts on the 85 is the easy route. If you're talking about the steel frome underneath it all being rough, and you don't own or have easy access to a MIG welder, Sawzall, Oxy/Acetylene and/or plasma torch, angle and die grinders, and assorted sheet metal fab tools, the time consuming but still doable wiring/engine/trans swap may be the only other option.