What are you using for mounts? I'm assuming for the Getrag, you used your existing ones, do you have a mount solution for the engine? Are you building your own?
As long as the axles go to the same spot as stock, and the engine is level and straight on the cradle, that's it. Good to go. There is plenty of room around the 3800 in the fiero bay (with the exception of the alternator, requires notching the decklid in its stock location).
Build thread for my 88 + 3800NA swap