SK,
Brake caliper clearance is an issue I am currently dealing with and it would be good to pass this info on to others too. I've bought 2 sets of wheels from Japan with supposedly the correct offset for an R34gtt but neither of them cleared my front standard brakes. It was only after a bit of investigation that I was told that the design of the spokes or X factor which some ppl call it affects whether a wheel will fit or not. The wheels I purchased were an O disk wheel (smaller brake clearance) when I should have purchased a wheel with R disk specifications (larger brake caliper clearance). I am getting 15mm bolt on adaptors made up as we speak. Will let you all know how it goes after I get these fitted as I may then have issues of the wheels sticking out too much! So the next time you are purchasing a wheel from Japan, take this into consideration especially if you have an R34GTT! If you have larger brake calipers in front then even the correct offset won't matter. I'm not a wheel expert and if anyone wants to add/correct what I have contributed please feel free.
Cheers