i do not know how much it weighs but i think no more than van as the box is constructed all aluminum rails and just tent. it is air ride you pump air to the shocks when havey load. yes i did 6K load but was not easy for me and for truck
Just checked the ram site, base curb weight of the 3500 cutaway is 4903 lbs so depending on the weight of the box, let's say 600 lbs, and it probably weighs more than that, so the gvw is 9350 minus 5503 is 3847 lbs capacity.
Now you know why carrying 6000 lbs made it unstable at 70mph.