Butt Ugly Chuck
Fish Biologist
31" tires are popular for stock suspension.... gives you a bit of overdrive without stretching it so much you loose ability to pull a grade. Some say 33" will fit with or without minor rubbing on full flex (depending on who you talk to), but that might make going to 4.11 gears necessary depending on your use.What size tires (larger of course) can you run with the OEM suspension without any problems?
Congrats on the buy! 17 MPG indicates a good running rig.

Butt