Ford F-150 VS F-350 Bodies frames steel alloys and thicknesses?

What are differences between Ford F-150 and F-350 Bodies frames steel alloys and thicknesses which could help F-350 to have more heavy duty body for towing and payload capacities?

Typically, trucks are built on the old fashioned body-on-frame design, like cars used to be before the 1980's. These were very strong, but made them very heavy vehicles. The modern cars are made from an unibody frame design, where the body of the car itself is part of the frame, which reduces weight, but also makes them a bit more trickier to strengthen. With the older body-on-frame designs, all you really needed to do to strengthen the frame was to add a few more crossbeams into the frame or replace them with thicker crossbeams, and you could largely keep the same body as the body wasn't really an integral part of the frame. Each additional crossbeam adds to the weight of the vehicle, but of course it makes the frame more rigid and stronger too. This is how quarter-ton trucks have been differentiated from half-ton and 3/4-ton trucks for decades now, so it's nothing new or high-tech in nature.

Oh, and of course the heavier duty trucks would have stiffer springs and bigger brakes too.

The F-150 and F-350 don't share much in common these days. They the bodies are different, the frames are different, drivetrain is different (different transmissions, transfer cases axles), different engines, etc.

Back in the 80's and 90's the bodies were the same, the frames were slightly different, but not by much, and major differences were the axles, and suspension. But since the late 90's they've been more different than alike.