I can only speculate on the GVWR rating Ford puts on the F450 pickup, but my guess is that Ford is deliberately keeping it in class 3 which tops out at 14K so that it won’t compete with the cab an chassis F450. My 2010 F450 pickup had a GVWR of 14.5K, and it was my understanding that was causing some unintended consequences since it was technically a class 4 truck.
The rear axle is rated by the manufacturer at over 14K, and as I mentioned earlier it took very little suspension modification to get the 2010 F450 to carry my camper the way I wanted. Those home-made stable loads I put on it aren't really that thick, especially when you compare them to the ones made by Torklift. The ones I made were as much to quiet the squeaking the overloads made against the rubber bumpers as to make them engage sooner.
Anyway, for my use the F450 is the better choice.
I brought the new truck home tonight.


My garage smells like a new truck now! :C
I haven't tried to back it under the camper yet because I need to get the tailgate off first. To be honest, after shoulder surgery that tailgate is just heavy enough that I need some assistance getting it off. Fortunately I have a small ceiling-hoist in the upper bay where the T-birds park that I use to remove the hard tops. Since surgery, I've been using it to also help remove the tailgate from the truck, and it does a great job.
It appears that the width of the new truck across the dually fenders may be a little narrower that the old truck, and if so I may be able to remove the "front jack swing-out extender extenders" that I had to install when I bought the 2010 F450. You can see them in the image below (the flat stock between the hinge and the jack tube). Keeping my fingers crossed about that.

EDIT: That turned out to not be true. The swing-out extender extenders had to stay! :B
:):)