I'll throw in my worthless 2 cents here. If you are concerned with the yellow sticker inside the door panel, you probably don't want a half ton truck. The safest bet is a 3/4 ton. The Ford 6.2, GM 6.0 and Ram 5.7 are all great gas engines for the 3.4 ton platform and aren't too God awful expensive. They will give you a lot more payload than any halfton, outside of the F150 HD Max payload/max tow package (which is darn near impossible to find and usually more expensive than a 3/4 ton... only worthwhile if you demand the Ecoboost engine, shich you don't want anyways).
That being said, my combined axle rating in my 2010 Tundra is 1000 lbs MORE than my yellow sticker says it is rated for. I honestly believe that the Tundra can handle close to a ton in payload with no ill effects. I don't advocate pushing a vehicle beyond its rated limits, even though I know that Toyota really unvershot their payload ratings. We were down in Florida last winter and I ran into a guy pulling a 31 foot fiver with a Tundra... from Michigan. He's done it every winter since he bought it in 2007. All he did was add airbags and E rated tires to prevent rear end squat.
Chances are you could buy a Tundra Crewmax, hook up that trailer and be 500 lbs over your payload rating and tow for 100,000 miles with great results. I can get 10.5 to 11 mpg towing on relatively flat ground if I keep it under 65mph.