The Nissan will not fit without major work and a lot of changes to the engine itself. The engine sets the wrong direction, entirely different fuel system, exhaust, cooling, you would need new wiring and custom programmed control systems as a start.
The Buick 3.8 will not work very well either because you would need to rewire the engine bay, change out the fuel system and custom make a new exhaust. The engine controller would need to be reprogrammed as well because of the changes. And it would need the older transmission because the current 3.8 you have is a different design than the earlier engine.
In reality the only thing shared between those engines is the 3.8 number. If you really are looking for more power you would be better off finding a bird with the V8 in it from the factory, those have a lot of performance parts available.
USER NOTES The info about the Nissan engine sitting a different direction is incorrect the GTR is AWD and the 380Z is RWD in which both cars have the VR38 3.8 Nissan engine
Monday, March 27th, 2017 AT 5:26 AM