SS8_ - The 18x9" +30 offset fits fine up the front on r34 gtt, I'd still recommend a minor lipping of the guards, depending how wide tyres are
dr1ft3r - use the offset calculator to work it out, I havent seen but I imagine the rear is a bit wide - definitely need to roll the inner lip on the guards with 265/35/18 tyres.
http://marksink.com/tire_wheel_offset/offset.html