I'm running the Toyo A/T 275/60-20 with no problems. Might be a little small for many around here, but so far I really like them. I've also got the 2" leveling kit with the ride-rite airbags in the rear. pics are in the gallery.

You can fit 35x12.50's on aftermarket wheels as long as they are close to the stock size. My aftermarket wheels are a 20" x 8.5" with 25mm offset (stock 20's are 20" x 8.5" with 44mm offfset).