Kypo is correct. Given the weight of the Cummins motor and the running gear on a 2500 you will have between 4500 and 5000 pounds on the Dolly and you will be pulling very close to 10,000 pounds with pickup and dolly. You will want a WDH and you want to make sure your RV can actually handle that much tow weight. RVs built on bus frames like the Prevost would typically have a 10-15,000 pound capacity, most RVs that are built on the other frames would not be able to tow that much weight, most are limited to about 5,000 lbs..
The Super C motor homes built on Freightliner etc frames can tow near 40,000