I thought I would pass this along in case your considering trying to stuff a bigger tire back there one day.
I have a 65 fastback and am running 275-50-15's. My car sits quite low, and the tires are perfectly centered in the wheel well. They touch ever so slightly if I push the car in a turn. I think a 255 or 265 is the limit, I just wish I could get a Nito drag radial in that size.
I have a '70 Mach. I was curious what the max size would be for my rear wheels. I have the standard axle housing with standard 4 1/2 leaf springs and Koni shocks. I thought 265-50-16's would be the limit?????? The size up from the 265's are 295's which are made by BF Goodrich. I haven't found another company with in between sizes. I wonder why? I would like to stay with 16's. Any thoughts?