I’ve got firestone adjustable airbags in my pickup with the compressor under the hood (99′ Silverado). I’ve got a pressure gauge in the cab and can raise or lower the back of the truck on the fly. This works awesome with my boat (Ranger 620).
I put coilover shocks and helper springs in my last truck and while it didn’t squat with the boat, it rode like crap unloaded. With the bags, when I’m done hauling the boat I just release the air and rides like normal.
They were installed on the truck when I purchased it so I’m no help with where to buy and install but I definitely recommend them.