I have the same truck but my camper is 8'6" so a little shorter than yours.
The Ram has the shortest SB of 3 manuf. at 6'4".
I just installed the Curt 2 1/2" receiver below the factory hitch. A very simple and straight forward install. It is a very heavy (80 lbs) and robust receiver with a 2700 lb tongue weight and 20k lb trailer capacity.
However, you will need an extension of around 32". I use my Reese 24" which is only rated for 600 lb tongue weight, but I'm not towing heavy.
I guess you could essentially make a "superhitch" design with the factory 2 1/2" and Curt 2 1/2" receiver and using 2 extensions.
For your application I would just get the Superhitch installed and not worry about it.
Another thing, if you haven't installed the tiedowns I would go with the Torquelifts.
I installed the Happijacks as I've had good luck with them in the past.
On my 15 Ram, the rear HJ fastened to the bumper doesn't seem as strong, but the front is ok.
If you have the 18" Firestones, you have over 7500 lb tire capacity so I would wait until after youre set up and weigh the rear axle before investing in wheels and tires.
I also installed the lower stable loads which helped but depending on your situation, you may consider airbags as well.
You will likely be around 3k lbs on the camper and 500-700lbs on the hitch. You will be close to max but OK. These new Rams are solid.
What engine do you have, Hemi or CTD?
