Best ride quality would probably be new spring packs. You could also just add springs but it will stiffen the ride. I have 1 extra leaf in the front and a few extra in the back and clear 33" BFG AT's on stock rally wheels with no problem, but every truck seems to have a bit of a different ride height. Leaving it stock I would say you could fit a 31 for sure, but then again I have seen stock half-tons run 33's with no issues. If you get into a swamper type tire that changes things though. My 33" TSL'S wouldn't come close to clearing but I could probably clear 35's in an all-terrain tire.