My 17x9's are 5" backspace and needed a 1/2" spacer to clear, and I run a 275/40/17. I have a QP 9" in mine though and it's about .5" narrower than the stocker. I'd say a 3.5" to 4" backspace would work on a stock rear without a problem. I do have rolled lips and a 3" rear drop too. On an 8" rim, a 255-275 tire would work. On a 7" rim, anything from a 215-235 should be cool. Use the measurements tire manufacturers give you to measure. My 275/40's measure 25.6" tall with full treadlife. you can get more tire diamater in with less offset, but only to a point, eventually it'll hit the outer sidewall on the lip. I think perfect for you would be a 255/45 and a 225/50. that's a pretty sick combo.