Here we go with wrong information again.
Paper payload is for taxation purpose and have very loose connection with actual truck capacities. That is why heavier diesel will have lower cargo rating as nobody wants to pay registration for what the truck can actually handle.
You want to be realistic - check rear axle rating, tire rating and then find how much the truck weights.
2017 Fords are about 400 lb lighter due aluminium body, so their paper rating went up. Actual as well and my dually carries 6500lb camper just fine