Hi,
My boss is looking for a supercab F-150 and I was looking at the Ford.com website for the truck he is looking for, so I could print out the window sticker.
I finally found a secret way to get the larger capacity truck. When I picked out F-150 then supercab, under the truck it said 'capacity up to 1800 pounds passengers and cargo'. By selecting the 8' long bed, it changed to 'capacity up to 3000 pounds' and I was impressed.
I think that you need to find a truck type of dealership that knows what to order in a pickup. I was able to find this by clicking on 'diesel' as a selection guide for finding a dealership near my home zip code that is near me, and also specializes in Diesel trucks. That dealership does not stock cars, but has a huge selection of F-250 - F-550 trucks, and many are already equipped with service body beds on them. So they know trucks!
You can play around with the Ford "Build your own truck" or just put in your contact information and ask the local Ford dealer to search for your truck, and call you with the specs. Be sure to tell them you are looking for the truck with (super cab, regular cab, or super Crewcab) that you are looking for. Color, and what options you might want. Towing package and brake controller should bring up the higher GVWR package.
You can get more information about the GCVWR in the Ford towing guide for 2015.
http://www.fleet.ford.com/towing-guides/Once I looked up "Camper ratings" on page 9 of the towing guide, it says to order payload package 627 and either the 5 liter or 3.5L Ecoboost to get the maximum GVWR of 7,600 pounds with a XL truck or 7,850 pounds with a XLT or Lariat truck. It changes it to a 3.73:1 rear axle ratio, and must also include the towing package. It includes upgraded springs and increased transmission cooling too!
Max GVWR and cargo weight rating with slide in camper are listed on page 10 of the towing guide.
Pages 16 and 17 have all the information about the GCVWR for trailers and the trucks.
Good luck!
Fred.