Tire and wheel opinions

On my 68 fastback;

What 72blunblu said. I managed to fit 15x8 wheels, can't remember the backspacing. I'll look it up when I get home. I fit some MT Sportsman ST tires at 255/60/15 with only a tiny bit of rubbing on the inside of the wheelwell when I hit large speedbumps with my old beat to hell springs. I completely clear the fender lip. I suspect that problem will completely go away when I get new springs.

Measure everything and do your math several times before you do anything though.