Use a 15 X 8" wheel with 4.5" backspace for a 275/60/15 tire. I am using 17 X 8 with 4.5" backspace and 255/45/17 tires on my 68 Camaro.
It is safer to stick to no wider than a 255 tire, but 275 will barely fit without rubbing.
It is safer to stick to no wider than a 255 tire, but 275 will barely fit without rubbing.

