The GVWR is 10300lbs, Max Payload is 1625lbs
Just curious where you got these numbers from? A 1500 Ram has a GVWR around 6800lbs and the payload with a rambox shortbox (crewcab?) is likely less than 1625lbs. A crewcab Laramie 4x4 with the rambox for example is only 1120lbs. What does your actual door sticker say?
As for the TH fiver question, you need a bigger truck. Even a conventional bumper pull TH that won't be over that trucks limits will be tough to find. Very few 1/2 tons are suited for towing fivers. Even fewer for a fiver TH.