Properly equipped the 3.5 can tow 12,000 lbs, but tongue weight starts to limit things to about 7000 regardless of the engine with 1/2 ton trucks. Ford does offer a heavy duty payload package that adds 800 lbs of payload, but those trucks are unicorns. If you can find one, or order one, there is some overlap with some 3/4 ton trucks.
Good point. However, if you look up the specs for the Ford heavy-half, it's nothing but tires, wheels, rear end ratio and extra springs. Plus you can only get them in the bottom grades, and not the crew cab.
A guy could "build" himself a "heavy half" for just a few bucks by starting with a 3.73 rear end, substitute heavier rated wheels and tires, and add airbags. You'd have additional payload capacity when needed, and the economy of the half ton instead of the 3/4 when not needed.
