I fitted R34 GTR Brembo’s to my R32 Gts-t and it's the caliper that has the thread not the hub, I just drilled out the hub-brake bracket to 14mm as there is heaps of meat left. I then just put on some R34 GTR 324mm rotors and it all lined up spot on and so did the R32 Gts-t brake lines.
So I think that the R34 GTR calipers will end up being to big for the 324mm rotors, as you Know R32 Gts-t are 280mm and R32 GTR ones are 297mm and so the bigger hub-brake bracket will make it 17mm to big for the 324mm rotor, so you might need to get some one to make up some 341mm rotors to make it work? Im not to sure but i hope this helps, Cheers