I had 33's on my truck with the 5inch lift and they were way to small. Went to the 35's and they look alot better. If you are going to go with a lift go with the 35's, if you don't lift it you should be able to run 33's with no problem. I ran 33's for 6months with no lift and really didn't have any problems.
99 F250SD Black Lariat Crew Cab 4x4, 5inch National Spring lift, 35x15.50 Swampers, 16.5x9.75 Weld Scorpios, Full Billet grill, LIne-X liner, Procomp and Rancho shocks, 40 Series Flowmaster, recalibrated speedo, superchipped,K&N filter,2 JL audio 10's behind rear seat, audio art 6channel amp