yeah shane would blab on about r33's and rb26's...and 32's and curse each one....maybe.
but yeah as i said above....if you change everything, then just placement of items and radiator etc, and tailshaft, gearbox mount are the only bits i can think of, but then shane may think of something else.....oh you may need to make room for the different style plenum off the 26, fuel lines.....fuel pump, dump pipes...should change straight off the other car.