I've owned 3 Class A motorhomes. A Gulfstream, a Monaco Dynasty, and the last one a Tiffin Allegro Bus. The Gulfstream had a 5.9L Cummins 190hp in it and it was VERY underpowered. The Monaco had a 8.3L Cummins, 325hp and it was adequate, while the Bus was powered by a 8.3L Cummins, 400hp and was terrific at all times. We always towed a car and I can tell you, you will appreciate an engine with torque in the 800+ range as these beasts are heavy and have a hard time "getting out of their own way".