Years ago I had one of those air mattress type deals that goes between the roof of the cab and the bottom of the overcab of the camper. It came with one of my campers.
All it did was wear the paint off the roof of the truck and eventually it popped one day when I went over a big bump that flexed the truck alot. I didn't bother replacing it and didn't notice a bit of difference in how the truck and camper handled without it.
Many years ago, I saw an old Chevy from the 70's ('73-'78 body style), it was a C30 Camper Special model, that had these little shocks mounted in the bed of the truck at the front bed wall that extended through cutouts in the front bed wall to the rear lower wall of the cab. I assume they were for damping the bed/cab movement with the camper. Never seen them before or since. Not sure if they were a part of the factory Camper Special package or not. My dad's '73 C20 Camper Special did not have them, neither did my '77 K20 Camper Special, or '82 C3500DRW Camper Special.