When we ran stock OEM 17" Load range E "10 ply" tires I ran lowest air pressures for "empty" weight as per the door sticker and/or the load according to the Load and Inflation Table for the tire. These tables are found on tire manufacturer's websites. Empty truck run at the door sticker "empty" load - likely around 40 psi rear as others have mentioned.
I use an air suspension coupler from AirLift to relieve the beating the 1 ton puts on a light trailer.
An air spring kit will not soften the empty ride whatsoever. I helps with leveling the truck when hauling loads.
A call or visit to one of the suspension companies like Carli will help you make a decision on possible things that will help. Make sure you describe exactly what you want the truck to do i.e. tow and haul on public roads, not race Baja...
These are trucks designed to carry weight so they aren't all that fluffy to ride.
