Ram crew cab 3500 will start you at ~4480lbs of payload in SRW.
Chevy crew cab 3500 will start at ~3900lbs payload in SRW.
Ford F-350 Crew Cab 350 will start at ~3930lbs payload in SRW.
These numbers are all for crew cab, 4x4, diesel, as I figured that is the most common truck most people shop for. These numbers are all before all your fancy options get added.
https://www.ramtrucks.com/assets/towing_guide/pdf/2016_ram_3500_towing_charts.pdf
http://www.chevrolet.com/silverado-3500hd-heavy-duty-truck/specs/trims.html
http://www.ford.com/trucks/super-duty/2017/models/f350-xl/
If I were in your shoes and wanted to stay SRW, I would probably lean heavily towards the Ram for the much higher payload rating in SRW configuration.