DON'T put the rears from the 350z wheels on the fronts of the rotas. you'll have to run 275/45 on the rear to keep the tcs happy, which is all wrong.
id go for 245/40/18 on the front, and 275/40/18 on the rear with those new widths.
but then again, the new fronts are only half an inch wider, and the rears an inch wider - with the standard 45 profile tyres, you probably wouldnt notice that much stretch.