Largest rear tire size

For reference, on my '65, I have 245/60 -14 on 6" aluminum slots with zero backspace. Springs are from a 340 '73 dart and the front has slant six w/air conditioning bars. No sway bars (yet!)

I only rub the rear inner-fenderwells (fender side, not the lip) in corners when the car really heels over or when hitting a large dip in the road at speed. I haven't tried it yet, but my mopar buddies tell me that I can "massage" the inner-fenderwells (fender side) to provide more clearance.

Going to 225/60-15 on 7" aluminum slots as an interum solution to the rub.