[OlympicFox]

A few thoughts. . .

First, while I didn't read all of the posts, the first half-dozen were spot on. A SRW F350 might be able to tow that 5th wheel technically, however it would not be a pleasant experience.

Second, as others have noted, the advertised cargo capacity of a truck is based on a stripped model. As you move up the food chain to a fancier model, there is a significant increase in the actual GVW of the truck with no increase in the GVWR or GCVWR.

Third, I'm sure that you have flown airliners that were full of fuel and people, as well as occasionally flown the same plane with only a handful of people and a light fuel load - the difference in performance is substantial. A fully loaded plane can feel like a dog, while the same plane with a light load is a joy to fly. The same holds true for trucks.

A new F350 may have somewhat higher ratings than our 2019 Ram Laramie 4X4 3500 SRW, however the real world performance is likely more similar than different. The numbers for our truck as built are:
GVW: 8,030#
GVWR: 12,300#
Payload: 4,270#
GCVWR: 33,610#
Max trailer: 24,870#

So, it seems that our Ram should be able to tow that Brinkley just fine. I wouldn't even consider it.

First, we need to adjust the brochure payload down a couple of hundred pounds to account for the Lariat trim level. Then, subtract for the driver, hitch, and anything you might want to carry in the bed. Now, you're down to 4,000# or less, perhaps much less. For example, we have a cross bed tool box for 'stuff' and a 50-gallon auxiliary fuel tank, and a heavy Trailer Saver air hitch. Suddenly, what looked liked ample payload is marginal, or worse.

Especially, for a 20,000# 5th wheel with a 4,000# or more pin weight.