Stock size is 275/70/18, which is equivalent to 33.2x10.2
But I am not lame, and 35s look perfect. Could probably even go bigger. Not even thinking about any sort of leveling gayness.
Its an 8000lb truck with solid axles and 65psi in the tires. Ride quality can not get much worse:D
Gooseneck issues are not issues with such a mild increase in tire size.