15X8 w 4.75 backspacing

440 Mike said
4-3/4 inch is just about the perfect backspace if you're using 4-1/2 inch conversion axles.

I believe the 255/70/15 or the 255/60/15's will fit. I found a conversion chart and punched in my current rim 15X7 with 1/4 inch back spacing with the 235/70/15 and the 15X8 with 4 3/4 back spacing with the 255/70/15's and I believe I'm going to be ok