2008 Ram 3500 DRW
GVWR 10,500 lbs.
Curb weight 7,801 lbs. = 2,699 max hitch weight
Front GAWR 4,750 lbs. (Front curb weight 4,575 lbs.) =175# additional weight on front axle
Rear GAWR 9,350 lbs. (Rear curb weight 3,226 lbs.)
Payload 2,700 lbs. (there's your problem. With 20% pin weight, your max trailer weight is only 13,500. Not nearly enough for a 20k 5er.)
Front axle capacity 5,200 lbs.
Rear axle capacity 9,350 lbs.
Front tire/wheel capacity 6,390 lbs.
Rear tire/wheel capacity 11,340 lbs.
Towing capacity 11,050 lbs. ( Stick shift lowers towing capacity to a max trailer weight of only 11,340)
GCWR 19,000 lbs. (minus 7801 curb weigh = 11,190 max trailer weight)
So no, that Ram cannot tow a 20k trailer. Maybe a 4500 Ram chassis cab, but not a 3500 DRW pickup.