with stock rims you can get by running a 37.. when you add an offset rim it will make them wider, hence harder to clear.. i ran 37 13.50 20 on stock rims with a 2.75" leveling kit and blocks in the back, it was too tight for me, shifted the axle too far, scrubbed and looked too narrow. 6 inches is minimum for a 37, imo, especially with any type aftermarket rim. if you want it to look good and still retain your gas milege,your performance, and part of your wallet, go with a 2 in leveling kit and blocks with 20"s and 35s