I think a lot of the bracket lift kits have a 3.75" - 3.5" max. backspacing requirement. That pushes the tires out wider and increases the likelyhood of rubbing due to the extra width. A buddy in my club had a '92 pickup and 4" Superlift kit, 3.5" b/s wheels and rubbed a little w/ 33x12.50s as well. He did a 2" body lift and then was able to clear 35x12.50s.