If your just in the market for new tires and want a slightly larger diameter then you could clear 33's but if you either plan on muddin or if you live in an area that has heavy snow or rough terrian, i'd have to say put a simple lift on your truck, just enough to clear 35's. Not knowing so much about smaller lifts for f-series trucks, before i bought my 250 psd i had a 1/2 ton dodge and put a 6" lift on for only 400 dollars... usually a 6 would have cost around 2 grand but if you take your time and do some good searchin online you will easily be able to put on a simple lift to clear 35's. With my dodge i put a 3" body lift and 3" block in the rear and new torsion keys so its was 3 body and 3 suspension and was able to clear 36 13.5 Super Swamper Iroks with no rub, then the jeep i put a 4.5 rough country then blocked the rear and coil spacer upfront. Think easy and don't spend 700 dollars on a 4" when you can do the same cheaper.