I suggest you check out NICOClub.com. Find the Z32 section, there is tons of info there.
I would also suggest to re-build the engine that is in the car. You can make a monster out of it, and check all components to make sure they are good. If you were wanting to get a drop in engine, look at Concept Z Performance, or Z1 Motorsports. They can get a front cut for you. They are also reputable companies. As well, there is Ztune.ca. They are located in BC and I've had nothing but great service from them.