I owned a 2009 Ram 4500 with only 305HP and 610 TQ... it'd pull a house all day and at speed. My new Super C RV has Cummins 6.7L 300HP and 660 TQ. OP had the same RV and said it did fine. HO is fine, but cant undersell the other Cummins 6.7Ls.
Just like G-Paw Sonnett used to say in the Sons of Will Sonnett: ... No Brag, Just Fact."
Cheers, Ron