Get a 06 that is the only year to even consider a 6.0 because with a 05 there is a chance it could have some of the problems the 04's had if it is a early enough production. Stay away from 07 just because you have to run ulsd vs lsd I know mostly everyone has ULSD now but in times of hurricanes its quite possible you will only have the option of LSD. I don't think you would be aware but when Katrina came through they had Off road diesel at all the stations and it was regular sulfur content. What price range and option truck are you looking to buy. I traded my king ranch 06 f350 and got 30k for it with 60k miles trading it in.
I would buy another 06 if I needed to It's never been to the dealer after I bought it except for a oil leak and when I traded it in I got warranty money back as I had miles left on the extended warranty. We had about 1000 f550 with 6.0 where I worked and almost all the 04's and 05's broke down a lot. We finally started getting 06-07's when I left and they were holding up a lot better. They were being used to haul 15k trailers and about 4klbs of wire in the beds. 6 days a week 10 hours a day. My 06 work truck had 1200 hours on the engine but only 10,000 miles so make sure the hours match up to the miles or it idled a lot and that is just like having a lot of miles.
I was looking for a 2005 or newer crew cab, 4x4, short bed due to the redesign in '05 with the new frame, updated interior, coil front suspension, and a newer version of the 6.0. After reading some of these reply's, I feel that I should look for a 2006 or newer, which I will start doing. The only diesel that is around here is ULSD so I don't think the sulfur content will affect me. I have experience with the 7.3, but I really want a newer model with the newer chassis, bigger brakes, smoother suspension, 5 speed tranny, etc. Problem is, there are no used trucks here in Gainesville/Jax that fit my budget of $25,000. I see there are a lot in O-town, but I'd rather buy locally for the convenience.