8.5 would fit on the back fine, I would look for the wheels with 8.5's in back if it were me.
It would look ok.... nothing to special. Although if you got them polished or somehow found a factory chromed version then that would look good.
I think the 300ZX wheels weight about 21lbs. So they arent anything special as far as light wheels but they are very good for the price.
Don sells spacers for out cars. @
PDM-Racing