Get the truck, load on the camper, and then evaluate what needs to be changed or added.
Oddly enough trucks have changed over the past 15 years and you cannot compare a 2004 pickup from any manufacturer with ones being made in 2014. Chevy greatly strengthened and stiffened its truck frames in 2011. Ram did the same in 2013 with its 3500 truck frames and in 2014 did the same for the 2500 models. This is reflected in the great payload and towing capacity for the new trucks.
I gained the most in terms of road handling with my SRW truck by upgrading the factory tires to ones with 20% more load capacity and so the sidewalls flex less with the camper load in the bed. The front ant-roll sway bar on my GM truck is the same diameter as the largest diameter ones from Hellwig so nothing to gain by changing it.
With a camper with a dry weight of 3200 lbs. in the bed the stock springs on my 2500 were able to keep the truck level. I added SuperSprings as I planned on adding gear, water, and other items to the camper, as well as a second battery.
Air bags are to be added only if all else fails. First see how the truck sits with the camper in the bed. If it squats add overload springs. Be sure that the tires will support the total load of the truck, camper, and what you will be adding for travel, including water at 8 lb per gallon.