I have the 15x8 with a 5.5 inch backspacing. Running at one time 26x10's and now the 28x10.5 et drags. Yes...you need to remove the quad shocks and do a little beating on the inside of the wheel whell for clearence with that big of a tire and rim combo.
I also heard you can run a 9, and 10 inch wide rim as well!
As goes for the fronts, I would recoomend running a 15x6. If your roads are in good shape and your VERY carefull you can even run the 15x3's or 4's in the front. I always messed them up driving on the streets. Chicago doesn't have that great of streets.
Good luck
P.S
Wouldn't you want to remove the quad shocks and put on aftermarket lower control arms anyway?
Oh, well good luck