[wadeh]

John,
My rear is 59 1/2" wide overall including the rotor hats. I had put in a Moser 9" that they said was a stock dimension replacement for the Mustang rear that CR had spec'd. On the inside, I've got about 1.5" between the sidewall and the bolts heads for the door latch brackets. I think I read that those bolt heads are what to look at for rubbing on the inside. On the outside, the tread just fits inside the lip. I would probably prefer about 1/2" more backspace to get it in from that outside lip a little more.
Wade