I'm going to get myself in trouble here, again.
IMHO, if you beef up your springs you can load it like a 3/4 ton and you won't have any problems at all.
Here is the "data" I'm basing this on. I work in an area that is populated with a lot of auto mechanics and body shops.
There are guys who make a living, such as it is, hauling off discarded engine blocks, fenders, heads, you name it. One such fellow has hauled off some stuff for us. He loads down his mid 90s Ford Ranger til the bumper is 4 inches from the ground. He'll pile metal up so high it is taller than the cab and over the cab. If there is an ounce less than a ton on his fully loaded truck, I'd be surprised. He does this day in and day out, as do a zillion other scrap metal collectors.
He's never had a problem, and kinda laughed at me when I asked him how often his truck broke down. "Never had a problem with it".
IMHO, the frame, axles, etc, etc, etc, on today's pickup trucks are way way way overrated. They are not going to fail becuause of a 50% increment in load. You'll need springs to hold it all up, and some good big tires, but the rest of the truck is tough enough to handle a lot more than the rated load.
This is merely my opinion, and I'm well aware that it is not shared by even a majority. Your mileage may vary. Void where not legal.