I carry a 4000+ pound camper and tow a 10,000 trailer with a '99 Dodge with Cummins, with zero problems - but it isn't stock.
What your truck will do depends... is it manual or automatic? Is the transmission stock? (Hopefully not, they're garbage when stock!)
Have you upgraded your fuel pump? Thats the FIRST thing you need to do to a 24-valve Cummins, the original is inadequate and won't provide enough fuel pressure to keep your injector pump cool.
You need an exhaust brake. The diesel provides barely any engine braking without one.
I can tell you a LOT about how to set up that truck to tow heavy but first I need to know exactly what you have.
Oh... and do you know about the dreaded "53" block in those early 24-valve trucks?
2017 Northern Lite 10-2 EX CD SE
99 Ram 4x4 Dually Cummins
A whole lot more fuel, a whole lot more boost.
4.10 gears, Gear Vendors overdrive, exhaust brake
Built auto, triple disc, billet shafts.
Kelderman Air Ride, Helwig sway bar.