working on a 68 barracuda fastback. have done a wilwood disc brake conversion, upgrading to 5 x 4.5 lug pattern. thinkin of going with a 255/60r15 on a 15 x 8" wheel on rear. looking for input on what may fit upfront. thinking of going with a 15x6" wheel. anybody have any input as to tire size and backspacing. thanks.