They're about dead on with a 31x10.5. I needed to lift my truck 1.5" (actually went about 2") to fit 31s comfortably. Of course, I have a 2wd sport which is one of the lowest sitting stock Xs. Seems about every X is different. I can tell that without the lift I would have had problems in the front at full turn, and in the rear at full "stuff".
You might want to think about doing a torsion twist/shackle lift. It costs $40 and gives you about 1.5-2" very easily without harmful modification to the stock components. If the lift leaves too much room, you can always go with 32s!
Good luck