Yes the Z looks bad *** with larger tires on the rear but I plan on going with the same size all around.

How about BFG KD 265/35ZR18 front and 265/40ZR18 rear on 9"or 9.5" rims? The fronts would be 25.3" dia. and the rear 26.3" to give me the stagger I need for the traction control system.

And by the way I weighed my rear 18" stock wheel without a tire and it was a very heavy 27lbs. Should be able to notice a quicker acceleration and shorter stopping distances with some good light weight wheels. SSR Comps or OZ Superlaggeras.