The ratings are really only guide lines. General terms.
Ford lists the F150 as having a GVWR of 6050lbs for a regular cab and 6250lbs for a Super Cab. Payload capacity will depend on how much the truck weights. Thus a truck with four wheel drive will have less LEGAL payload capacity than a two-wheel drive if it has not been equipped with optional springs to compensate for the greater weight.
Ford lists the F250 as having a GVWR of 8800lbs. The payload capacity is listed as 3740lb for a regular cab 2wd and 3200lb for a reg. cab 4wd. The other end of the range is a LWB Crew cab, which is rated at 3055 in 2wd and 2645 for a 4wd.
The F350 having a GVWR of 9900 lb. in single rear wheel configuration and 11200 lb. with duals. Duals give the same truck a capacity of 5875 in 2wd and 5465 in 4wd.
The F450 has a GVWR of 15000lbs. The Regular cab 2wd vs. has a payload of 8765 and 4wd 8435lbs.
The F550 has a GVWR of 19100 lb. Payload will depend on all kind of things like options, body weight et.
The F650 has a GVWR of 26000 lb. Again payload depends. While I like Fords, anyone who tells you that the diesel in a Dodge Ram won't pull is kidding themselves. This truck uses the same Cummins ISB that Dodge uses in their pickup with a higher torque rating!
The F750 has a GVWR of 30000- 33000-lb. This truck can be equipped with the Cummins ISB or the CAT 3126B.
So relax, mctree, i made it clear in post #8 "one ton chassis archetype."