I went round and round with this when I leveled my 4X4 2010 QC by 2". There are some good topics on wheel/tire combos in the forumz. Do a search for leveling kit and you will see some good topics pop up.
I ended up putting on 33" (specifically they are LT 275/60R20) ProComp Xtreme MT's without any rubbing problems. The tire is actually only about an inch bigger diameter than your stock tires. The 33" tires fit perfectly on the Stock 20" Chrome Wheels. The guys at 4Wheel Parts said that you can probably get 35's to fit but you will have rubbing issues when turning. With a new truck, I did not want to start trimming fenders etc.:Wow1:
Let me know if you want a pick of the setup and i can post it for you. The tires are now on Fuel Hostage Rims, but the overall setup is pretty much the same.