66 Barracuda 18" fitment question

Well, figure out the backspacing of the wheel. If they're the Mustang, Torq Thrust looking wheels, they should have some castings on the back of the spoke that state the size. I don't know early A's too much, but I'd assume you should be able to get a 245/40/18 with the proper backspacing on all 4 corners. Are there any big differences in the wheel well or front quarter panel between the early-A Barracuda's and later A's? Personally, I'd just do a bbp swap if I were going with those wheels.