It has to be the rear half of the 2 part drive shaft from a r33 gts-t with the rb25 the same car also has teh 5 speed tranny. it also HAS to be Z31 rb20 eng mounts. and everything bolts in. just the tranny mount had to be fabricated. I would not attempt this unless you have a friend in japan that can verify parts you are getting.
BTW when i posted this back in 2002 that was the only option unless you made everything yourself. there are now a few other options that would be less risky and probably be cheaper when you factor in shipping