I was able to look up a DRW Crewcab truck that was a BASE Truck, no extra options like leather seats, ect.
THE front axle was 4,183 and rear 2968 for a DUALLY 6 liter GAS engine.
To add the diesel option you add 633 pounds to the front axle and 66 to the rear one.
This is done for each option that you pick. I was not able to pick out the correct truck SRW in your case, however I think you might be able to. Just I don't want to spend time researching your truck. . .
So you have a "Guess" on what the rear axle weight will be on the truck you are looking at. 3,100 pounds or so. It should be within 300 pounds of that weight. (2,800 to 3,400 pounds for a single rear wheel diesel truck.)
Good luck!
Fred.