With gas prices as they are, I'd shoot for an older half ton with the 350. I know a guy who's got over 250,000 miles on his, and it stills runs strong. Granted he doesn't tow anything...but they're good rigs. The main reason I suggest it though is that he gets 20 mpg on the highway when not towing. With the 35 gallon tank, that's a 700 mile cruising range. That's Moab and back with fuel to spare. It wouldn't be the best choice if you're going to tow heavy loads...but for ~5,000 lbs, it would be fine. The only potential downside that I see to the old 5.7 'Burbs is that the newest one you'll be able to find will be 6 years old. I don't have any experience with the 5.3 'Burb, but again, for relatively light trailering loads, I would think it'd be fine, and it should get decent mileage when not towing. If you plan on towing more often, or heavier loads, I'd go for the 6.0. It has the power, the heavier duty trans, axles, etc, and the leaf spring rear end (vs the 5 link coil on the 5.3 1/2 ton), but it's still a small enough engine that you should be able to get decent enough gas mileage. The 7.4 and 8.1 are awesome engines, but they suck fuel like a Hoover sucks dirt, which doesn't cut it when you're paying 3 dollars a gallon.
