i have 18x9 bullits mounted on 265/35/18 in the front and 18x10 deep dish bullits mounted on 285/35/18 in the rear...so i'm guessing those tires will work just fine...however, i prefer larger tires in the back so maybe swap those 255's for something in the 285-315 in the rear...i think it'll give the stang a much more sinister stance
