The late '90s/early'00s 2500 Dodge/Cummins 4x4 std tranny of that era were using the Dana 80 rear axle. Auto tranny trucks generally had the Dana 70. So forget about any rear axle overload issues with this truck.
These 2nd gen trucks have very stout rear suspension complete with a aux overload spring pack so they will carry 6084 lb on the rear axle with no problems. Many add air bags to rear axle to increase payload capabilities or eliminate any sag.
Those old 2nd gen trucks were light on the rear axle with generally 2700-2800 lbs dry weight which leaves around 3200-3300 lb for a payload. Trailers add little to no weight on the trucks front axle so its not a big player carrying a load.
The '99 Dodge/Cummins weak link was the 47RE tranny unless it was uprated with aftermarket towing goodies. How much can the truck tow. Keep in mind the truck is 17 years old so it won't have the high tow rating of the new gen trucks.
Some of the 2500 Dodge 4x4 trucks in '99 had up to 13600 lb tow rating depending on gear ratios and auto vs manual.