A 1/2 ton truck is not just a 1/2 ton truck. Customers demand that they ride great, handle great, brake well, handle well--and they want them to tow extremely heavy loads. It's just not possible to be everything for everyone, and most 1/2 ton trucks have the springs of an old Ford Crown Victoria.
Very few 1/2 ton trucks are equipped with manufacturers' heaviest duty suspension and camper packages. They must be secial ordered in most cases.
For 2015, the new model F150 with the maximum suspension package will handle much more hitch weight/pin weight of any other manufacturer--that approaching a 3/4 ton truck. The package is approaching $2K in total costs, however. You'll also want the 3.5 Ecoboost engine, which is expensive in its own right. GMC/Chevy and Dodge are close in weight capabilities--far below Ford. I've not looked at Toyota specs., however.
When you add a crew cab and 4x4 options, weight carrying capability goes down and down--due to the weight of those options.
I would seriously compare prices on a gas V-8 3/4 ton truck vs. the heaviest duty 1/2 ton trucks. There may not be much, if any, price differences, and the 3/4 ton suspensions and brakes are far stronger than that on 1/2 ton trucks.