Is your toy hauler 20k or 36k? You mentioned a 15.9k lb payload on top of the trailer. I'm not aware of any toy hauler with tires and axles rated for that much. I believe the largest ones I've seen have 18k lb gvwrs.
Payload capacity is not your main concern with the trucks above. But if you're really going to pull the kind of weight you are talking about, you may need a special license. And no way those trucks weigh 7k, even empty. With a bed they are going to weigh twice that or more.
Post the weight ratings for the trucks (GCWR, GVWR, and empty weight of the truck full of fuel, and we might be able to have some clue if a truck that big is necessary for you; I think not.
1 ton trucks have payload capacities of nearly 8k in some configurations and the 550/5500 series trucks have much more than that, way beyond that which is necessary for 3,200 lb pin weight which can be handled by any modern 1 ton dually and even some single wheel trucks.
Toy hauler 20k GVWR (three 7K axles)
PLUS Payload about 16K that I want to in the back of the truck.
So need to tow 20K and haul 16K at same time.
To reiterate:
F-650GVWR 29K (needs upgraded suspension)
GCWR 50K
Curb-weight: 12K
International CVGVWR 22.9K
GCWR 37.5K
Curb-weight: Not sure
As for as license, I will have to get Class A Non-commercial license that permits me to operate over 26K