What is the widest tire that will fit a stock 1973 corvette

I have a 295 X 50 but had to put on modified L-88 flares to keep from hitting the fiberglass. I have 265 X 50 on the front w/o any modification. They will fit on the back also. These are on 15" rims. I have seen large T/A radials 265 X 60 fit inside and it fills the fender wells.

And on the car.

uh...if you had to modify...that's not the widest tires to fit on a "stock" 1973 - which was the question