I dinghy tow a 3/4 ton CC Silverado with a Polaris RZR in the bed. Never got a fully loaded weight but I would guesstimate at 8,000 lbs. fully loaded. I have 275 HP so I will never set a speed record but still plenty of power to go anywhere I want.
I am certainly pushing the limits of my DP as you will be but it can be done and done safely. Reinforce the hitch and frame as needed (remember almost no tongue weight when flat towing just pushing/pulling forces), expect slower acceleration and hill climbing, stopping may be a little longer but I see/feel no difference. I find myself having to look in the camera just to confirm it is still behind me. And then the obvious make sure the tow bar is up to the challenge, auxiliary lights on the truck, and some sort of auxiliary brake system for the truck. Length can also come into play. I have a 36" DP and with the CC short bed hooked up I am just under the 65' mark.
Also one thing that can affect tow ratings is which Allison you have. A call to freightliner revealed that my DP was rated at 5,000 lbs. towing because of a 5 speed 2000 series Allison on the Fleetwood spec. sheet which was not accurate. I have a 6 speed 3000 series which according to freightliner would have allowed a 10,000 lb. rating.
