I'm in kind of a pickle with my tire situation. I'm considering selling the stock wheels and tires and running 19.5/22.5s due to the longevity. Basically I have a stock F-350 CC DRW truck and the dealership I bought it at replaced the front two tires but not the back 4. The front two are pretty much brand new and 3 of the back 4 are in good shape and have a really good amount of tread and one had a wheel weight get knocked off and is all FUBAR'd. See poll for my potential courses of action.
I am all about the 19.5/22.5 options. If the front are new, I would not discard them. And the backs are going to last longer than the fronts anyhow. I would replace the rears, on stock rims, and bank money for a full set of rims and tires..... which are fokkin expensive..... but if you part with a few hundred now, for 4 rear tires, then bank for a year or 45,000 miles.... you will have had plenty of time to get sorted out. Also, the 10 lug rims off of a 450 will require adapters for your rig. And the 22.5s will require a DIFFERENT adapter.... the bolt pattern is NOT the same... a few companies, Vision Wheels, American Force, etc, make direct bolt on, 8 lug 19.5s for your rig. That is the cheaper way to go. No adapters (900 bones) required... I would stay with 19.5s. I have em, (stock) on my 450, and upsized to the 245 and 14 ply from the stock 225 12 ply, and after 41,000 miles, I can say that they are going to last me 100,000 miles..... Easy. But I would NOT get the mud terrain tires again. Horrible ride. At least, on the front tires, I will get highway tread, not even all terrains...