For years 250/2500 and 350/3500 SRW have shared 99.9 percent common parts. Duallies only differ by narrower rear diff housing, different wheels and tires, front wheel adapters, wide hip fenders and sometime rear spring pack. Ford's in certain years the difference was the spacer block between the rear axle and springs. For GM it was rear springs and sometimes tires. For Dodge it was overloads and now the 3500 actually has less but heavier leafs. Dodge built 2500's from 2000 to 2002 with camper option that made them just like 3500 SRW trucks but did not label them that way or increase the GVWR. Russ' and mine were built that way.
So before you get to carried away, realize they are basically the same truck. Built on the same assembly line. The load limit imprinted you the tires is the most legal and binding weight number you will find on the vehicle. Typically the RGAWR is two times the tire rating. The FGAWR tends to be set by the axle/springs. My state Washington, could care less about the GVWR and licensed my 2500 by their required formula at 12,000 lbs.
It would be very difficult for a pickup to exceed federal bridge weight laws. If you want to understand this more, go talk to a hotshot hauler at a truck stop. They would roll on the ground laughing at some of the things RVer post about pickups. No one is putting them in jail and throwing the keys away for being over weight and they are required to stop at the chicken coops and be weighed.
Chris