Atfer a quick search, I found that a few people have fitted 265/35/18 tyres to R32's, so you may not need to go to 235's:
http://www.skylinesaustralia.com/forums/in...showtopic=79629
http://www.skylinesaustralia.com/forums/in...showtopic=84208
Using a +20/22 would be a safer bet as you could always decrease the offset slightly if need be.
I'm still trying to work out how to fit 18 x 11's