The badge on the door reads "Ram 3500 Heavy Duty" with no mention of the chassis cab. The lack of a pickup bed makes the latter obvious, and since the text on the badge is similar to that of current pickups, it's safe to assume there'll be future badges on which the 3 becomes a 4 or 5 (see "Max Payload, page 10).
That the Chassis Cab 3500 may lead to heavier versions is a poorly kept secret. When was the last time you saw a mainstream vehicle with a platform that wasn't shared with something else? Besides, Chrysler doesn't have the funds to toss at new platforms. The medium-level commercial market sells about 100,000 units a year, easily large enough for Dodge to get a piece of that pie. Not only that, but Dodge wants to have something to offer to the guy whose trailer or business outgrows his Ram pickup, and a Sterling or Freightliner are too big. This chassis cab contains Dodge's other big news: the 6.7-liter ISB Cummins diesel. It's optional in this truck and in 2007 calendar year Rams, but they aren't identical engines.
Truck-body builders worry about only two things with cab and chassis setups: payload and ease of use. Its weight is about the same as a Ram pickup's because the sturdier components offset the lack of a pickup box. The Dodge rails are industry-standard C-channel beams 34 inches apart with little hanging off the sides except rear leaf perches and nothing--not even a vent tube--standing above the top of those rails.
The large fuel tank is behind the axle, well skidplated and tapered up to the underside rail at the tail, so it shouldn't affect departure angle or drop platforms. Local delivery types who want more payload or to mount power equipment in the back (both transmissions offer a PTO) can opt for a 22-gallon tank inside the rails ahead of the axle in lieu of the big one.
The Chassis Cab comes as regular or Quad, though only the standard cab gives the choice of a 60 or 84-inch cab-to-axle length; fitting an eight-foot box onto a 60-inch Quad Cab is no problem, and fifth-wheel or gooseneck pullers shouldn't have clearance issues. With commercial design comes narrower-track dual rear wheels, four-wheel-drive models add a differential and axle shafts to the solid front axle, and max 23,000-pound GCWR means you can add a custom aluminum bed and pull a 15,000-pound trailer. Just as heavy-duty pickups have progressed to the point that driving them empty doesn't mean a punishing ride, these ride well with just one ton of bodywork over the rear axle, and the steering doesn't feel noticeably less communicative than on the independent front end.
Two reasons Brand F sells so many medium-duties are the pickup-truck cab that goes with Ford's models and lower height than most TopKick/Freightliner/Peterbilt-size trucks. To that end, you can get a Ram Chassis Cab with most of the luxo features available on Ram pickups, and little of that should change when a 4500 or 5500 series appears. Bigger springs, brakes, axles, and 19.5-inch wheels are easy to come by; there's no reason Dodge shouldn't offer them on the Chassis Cab.