What can a Ram 3500 (6.7 Cummins HO DRW, gooseneck) ('19-24) actually tow?

The rating is the easy half of the answer. A trailer never weighs its brochure dry weight — water is 8.34 lb a gallon, propane and batteries ride along, and so does your gear — and hundreds of models changed their published weights mid-run, so the model year decides as much as the model. Judged that way, with a 10% margin and 2 people aboard: 5150 of 5150 campers fit a Ram 3500 (6.7 Cummins HO DRW, gooseneck).

The number that quietly binds is payload — 6,560 lb (Ram 3500 Regular Cab 4x2 DRW 8' bed, 6.7L Cummins HO/Aisin, 4.10 axle, 14,000-lb GVWR, 45,000-lb GCWR - the row that carries the 37,090-lb rating; the 13,500-lb GVWR build also reaches 37,090 but carries only 6,060 lb): tongue weight lands on the rear axle with your passengers and the hitch, so a vehicle often runs out of payload well before it runs out of rating.