I would say chatting with the Great Folks at Timbren would have been in order. When I talked with them they recommended the NON HD model with my Eagle Cap 950 Camper and LWB SRW FORD F350. I do question the use of Timbrens on a Dually. I used Air bags on my previous two trucks and campers. Didn't like always having to adjust the air. Now with the Timbrens I have 1 inch of axle bumper clearance when the Camper is off and a very nice ride and a level ride with the NON HD Timbrens and the Camper loaded. I do use a Hellwig Big Wig Anti Sway Bar as well. I am very happy with the Timbren Enhanced Suspension System.
GARY