I have the 275 HP 660 ft.lbs. torque cummins and tow a 3/4 ton 4x4 chevy with a Polaris rzr in the bed. I also just inherited a 2015 ford f 150 that I am going to set up as a toad.
It can definitely be done. You won't be the fastest to the top of the hills and acceleration will be a bit slower. Dinghy towing is not the tongue weight but the pushing and pulling on the hitch. Find a good welding shop and have them reinforce the hitch.
I am underpowered but the 6 speed Allison definitely makes it doable. during my research I found that a 5000 lb. hitch was installed as most of the units at that time had the 5 speed Allison which limited it to 5000 lbs.. The chassis was rated for 10,000 lbs..