Go with the 33" tires if you want to 4wheel... These trucks have very little clearance stock and will bottom out. Tires are the best way to avoid this. The best way to fit the 33" tires with out rubbing... is a 2" body lift. Cost $115 if you do the install (takes a day). This gives the truck a nice look too!!!

Here is a pic of my truck with the body lift and 33" Super Swampers (also 3" Suspension lift). It looks much cooler:

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