What you guys are asking for doesn't exist and is not likely to ever exist. The basic laws of physics and DOT truck definitions, marketing factors, and more are the reasons it is not likely.
In order to offer a truck capable of actually carrying a 5k or 6k payload, not a brochure truck like Furd offers, the truck will require much stronger frame, suspension, driveline, axles, brakes, and wheels and tires. Those components will be heavier meaning the unladen weight will be much greater. The theoretical new pickup you're asking for will weigh around 10k lbs. empty and with a 5k or 6k payload will have a GVWR of 15k to 16k which means it is no longer a Class III truck but a Class IV truck. Class III trucks by DOT classification cannot exceed 14k.
A Class IV truck will of necessity ride like a truck or like the current Ram 4500 and 5500s do. A Class IV truck will also create different licensing, registration fees, and in some cases insurance issues. Demand for such a truck is not sufficient for Ram to spend the money to develop a modified pickup bed to fit or it would already be on the market. Not very many prospective owners want a Ram pickup which will ride stiff and cost several thousand dollars more.
Furd doesn't and never did offer a genuine truck capable of carrying those payloads. Furd used brochure engineering to achieve those load carrying claims. The F-450 pickup of today is nothing more than an ordinary F-450 with an extra leaf or two in the springs. The previously offered F-450 p/up did have 19. 5" wheels and tires but no longer does.
You can't have a soft cushy ride and 5k or 6k load capacity. More truck is required.