We upgraded from a 19′ Airstream to a 23′ and the extra tongue weight was causing the rear of our truck to seriously squat even with the aid of a weight distribution hitch. For whatever reason, it took Firestone ages to finally release a kit that works with our truck but I am glad I waited. The installation was straight forward and has dramatically improved the rear end squat. On the 4×4 Diesel at least, the drivers side installation will require two people to do the install. The inside bolts are very tight between the subframe and gas tank. I needed a helper to hold the wrench on the top nut while I used an extension from the bottom to tighten the nut
The kit you need from Firestone is 2587 “Helper Spring Kit”
The Kit can be found on Amazon
At 20 psi unloaded this kit raised the rear by roughly an inch. At 60 psi unloaded this raises the rear end by roughly 4.5 inches which is basically what I need for when I have the Airstream attached. This system can be pressurized up to 100 psi. Firestone offers a ten year warranty with this setup which is nice.
Pair that kit with a union tee and you can air both bags from one point.