Mine are 20x10F & 20x11 rear. They sit more or less flush with the fenders without the need for any spacers. You will need hub rings though (how many depends on a couple factors such as style # and whether or not they're reps or the real McCoy)

Also, regarding the 21" wheels, you may need flares from the 4.8is as the tires that you'd normally wrap them suckers in is a 325.

__________________