Considering new truck

Ahhh, the ole cart before the horse.

Your payload on a SRW is based on the GVWR, minus the weight of the truck as it left the factory. To get the highest door post sticker payload, you would have to keep the fancy options to a minimum, as everything adds weight. I would suggest to get the highest rated tires/wheels available, as they are the true limit on the RAWR, which is a big concern with 5th wheel pin weight.

Jerry

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.

I would echo what Farmerjon said. We recently traded our '13 GMC 2500HD for a '12 F-350 DRW (actually had 3,000 less miles on it than our GMC). The reason we did this is because, with a SRW truck - whether 2500/250 or 3500/350, you run the risk of reaching the max load limit on the rear tires of the truck very quickly with a single rear wheel and a fifth wheel. Look at the GVWR (not the published dry weights or pin weights) of the wheels you are considering and take 23% of that GVWR for an estimated loaded pin weight. Our loaded "mid-profile" fifth wheel (13,990 GVWR) rolls across the scales with 3,100 lbs on the pin. We are MUCH more comfortable with the DRW truck. As for brand, see if you can find a truck with the Cummins turbo-diesel, the Allison 1000 transmission, a GM chassis and front end (steering), and the Ford interior and body. In other words, find a DRW 1-ton truck you like and get it.

Rob

The highest payload will be a regular cab base model with gas engine. Bigger cabs, options, and Diesel engines eat up payload.

We tow with a 2016 RAM 2500 6.7 diesel. I have towed with Fords F250 Power Stroke and Toyota Tundras. My experience with the RAM so far is very good. The Cummings diesel is rock solid and pulls well. The 6.7 4WD is rated at 23000 lbs towing capacity. We have a tow behind 32 ft hitch to bumper and hardly ever know it is back there. We live in the central valley and cross the ridge route often. There are two steep grades and the truck handles both the up hill and down very well. The smart exhaust break is a feature that I really like in the mountains.

Since I am totally unbiased ,hah:B I would suggest you stay with Ford.
I think any of the 350/3500 would be a good choice.
But I would seriously think about a dually, they ate rated higher and are more stable.
have fun in your search.