my dad ran 325/65R18 goodrich KO's on aftermarket wheels. I think 18x9s with 5.5 in backset. they did not rub at stock height, but did when he put the leveling kit on it. If you pull the plastic out of the fender well there is a large flange where they joined 2 sheets of metal together that isn't trimmed very close at all. You should be able to grind 1/2 an inch off, probably more, and fix any rubbing issue you might have. Sorry I don't remember the specifics, its been 2.5 years since we did that. You might have to a) drill a hole and use a push stay to keep the plastic far enough back, or b) drill 2 holes and use a zip tie. We did that on a few trucks that the tires rubbed on.