I don't know about other trucks, but the differences between a 2015 2500HD and 3500HD SRW are two things: one overload spring that doesn't even come into play until you are north of 6k on the rear axle, and the 2500HD comes with 20" wheels that aren't even an option on the 3500s. The 3500HD SRW and DRW suspension are the exact same. The axles are the same. The brakes are the same. Everything is the same except for the hubs and wheels/tires. You have three setups that are basically identical, and the only things they change are the wheels and tires to change the amount of weight you can put on them. The stock 2500HD tires are rated for 3100#/ea, 3500HD SRW rear tires 3525#. They don't provide wheel ratings, but one can assume they're pretty close. So from a technical standpoint, putting 3500HD SRW wheels on a 2500HD and adding an overload spring (or yes, airbags - because they will effectively do the same thing as an additional overload) will give you the capacity of a 3500HD SRW. Technically. The sticker won't say it, but parts do. Since the entire 2500HD-3500HD line is the same, except for wheel/tire configurations and a single overload, that means you can move up into dually territory with these trucks if you are careful about it. Rickson and other companies make 19.5" wheels that allow you to use G or H rated 16 ply tires that give you not only the weight carrying capacity of a dually, but the stability due to the thicker sidewalls as well. That's not without downsides, and perhaps legally questionable, but there aren't any physics saying that you can't push a 2500HD into dually territory safely, with the appropriate modifications.