I haven't researched this for an R33 to be honest, but from what I know, you'll just need the 5 stud hubs and get your current rotors re-drilled, but I would recommend upgrading to the larger 4 pot brakes as well so no need for the re-drilling.
So to upgrade to the larger brakes and 5 stud, you'll need the hubs, rotors, calipers and probably a new master brake cylinder. There should be a few threads in the NA section of the forums with the information you're after.