I am surprised no one with a early Barracuda has commented yet. Someone will I hope. THere has to be someone in this group that runs 15x8's with a 255-60. Both are a common size. The tire will just look a little fatter on a 8" wide. Going from a 4 to a 4.5 backspace will add 1/2" to the front and back but a half inch is barely noticeable on the outside if you are wanting 8's over 7's just for looks.