69 valiant rear 1/4/tire and wheel measurement

well gentlemen...i put my cousins 28x10.5 mt slicks on which have the cop steelies (i believe is 4 and 1/4 backspacing) the fact that i have super stock springs and drag shocks, i dont have to worrie about fender lip as much...so i think 4" would be good....i also only have 245/6015's which is a little thinner than the drag tires...