2015 Ram Trucks

The overhead cab over clearance verses cab roof is based on deck height. A chassis cab has straight frame rails that ride higher than a pickup frame, so the bed deck is higher. This gap is also affected by cab height - The Fords have the tallest cabs and I think GM's is the shortest. The gap between the back of the cab and camper is dependent on deck length and whether the camper was designed for a short bed or long. My Arctic Fox is designed for a short bed yet is sitting on a 9' deck.