I ran 15" uni-lug Crager SS on my 69 B'cuda for well over 20 years BB stroker,4spd, 3:73 sure grip. Never had one come loose.

To help with the OP's question....my car is a 69 FB with big bolt pattern. The Cragers I ran were 15x8 rear(4" backspace) 245/60 tires. Fronts were 15x7(3.5" backspace) 225/60 tire. Cleared fine....likely could have done a 255 tire in the rear but never tried. I run a 255 now but it's on a 15x8.5 wheel with 3.75 backspace.