From the 2013 Ford Super Duty towing guide:
SRW limited to 3.21 or 3.55 axle ratios. Neither are available with limited slip (though electronic locking is available).
F350 DRW has 3.73, F450 DRW has 4.30 ratio.
Long bed gas tank is 38 gallons vs. 26 for short bed.
Tailgate height is 3 inches lower on the DRWs than the SRWs.
Gross Combined Vehicle Weight Ratings (truck, trailer, fuel, passengers, cargo combined):
F250/F350SRW - 23,500 lb.
F350DRW - 30,500 lb.
F450DRW - 33,000 lb.
SRW limited to 3.21 or 3.55 axle ratios. Neither are available with limited slip (though electronic locking is available).
F350 DRW has 3.73, F450 DRW has 4.30 ratio.
Long bed gas tank is 38 gallons vs. 26 for short bed.
Tailgate height is 3 inches lower on the DRWs than the SRWs.
Gross Combined Vehicle Weight Ratings (truck, trailer, fuel, passengers, cargo combined):
F250/F350SRW - 23,500 lb.
F350DRW - 30,500 lb.
F450DRW - 33,000 lb.