I'm finally making up my mind about which wheels to get (I'm still not 100% sure...). The reason I think I'm going with the TTD's is because I've seen to many 71-73 stangs' with the Mag 500's. But, my question is, would I have to make any backspacing mods to put 15x8.5? If so, is it difficult to make this mod (I'm not quite sure how the backspacing works)? Thanks!