Just bought a 2021 F350 diesel/4x4/3.55 Axle/12,000 GVWR/Crew Cab/ 176" bed with the Ford 5th wheel hitch package. Just purchased a Jayco the RV with a 3,250 lbs. dry hitch weight and a max loaded weight of 16,250 lbs. I have two issues.

1. Ford spec's show a payload capacity of 4,190 lbs. for this spec truck. The sticker on the door frame shows cargo+ passenger capacity of 3,485. What am I missing?
2. Bought the Ford Accessory 5th wheel hitch package. After getting the truck I was looking at the 5th wheel manual I found and it's showing the published 19,000 lbs. tow capacity but only a 2,850 hitch capacity. Why the limitations compared to the hitch that Ford gets from Reese (see below)

I believe the Ford hitch is manufactured by Reese. I called the Reese factory and the customer service rep looked up the Ford OEM hitch that Reese sells to Ford. It is the same as the M5 puck style that has a 20,000 lbs. tow rating with a 5,000 lbs. tongue weight capacity.

I bought this truck with the special GVWR of 12,000 lbs. with the long bed so I'd have extra cargo capacity. Can someone explain where I went wrong or what I'm missing?

 

Believe the 3,485 number you read as the real cargo capacity. It is the "As Built" capacity. You have to look at extras added on including the extra weight of a diesel motor, sunroofs, hitch, etc. Sadly that's where a real wakeup call sets in! Can't tell you about the Reese hitch though. I know most people on the Grand Design forum (RV mfr) are using the AHU with the pucks. It's around 60lbs. Not sure how that compares to yours. Either way, that still puts you without much for extra cargo capacity! Once you start to load up the 5er you will be at ( or over) capacity without anyone/anything loaded into the truck.
We have a 2020 F250 with a 2,940 cargo capacity. If you look at the specs for that truck it was 3,470 before options were added on. We then went after the 5th wheel that was well within our truck capacity.