Okay so i have 17"9" wheels right now and im thinkin about upgrading my rear ones to 18.9" will that be to big of a size difference sinc my fronts would only be 17.9 and the rear 18.9? Another question i have is i lost a center thingy to one of my wheels which are like 2000 cobra replica wheels so i was wondering if the cobra r center thingy would fit because on Am it says does not fit saleen or cobra wheels.