I was wanting to know the same question your asking but I do think the axle does. shorlineF150 has the same thing I think give him a shout, I know he narrowed his axle but not shure if he has the same backspacing as you?
tyler i dont know if it will cause right now i have twentys that are 8.5 wide and the tire is really close to the bed. in fact the way the side of the bed is if my wheel tire combo was an inch higher it would be hittin the bed. good luck with it though
eh im planning on running billets anyways eventually, i had just come across some pretty cheep chrome 22s with that backspacing that i would have liked to run temporarily but oh well