[dwaite72lnghrn]

Personally I think 1/2 tons are good for 4000lb with 3.73 gears and an auto or 4 speed stick. Air bagged I would lessen the load as the rear would be squirrelly. This is for towing on a regular basis. Once a year OK go heavier. Remember you should have about 10% of the towed load on the hitch and 400lbs added to the rear of a 1/2 ton is alot especially when you add in side winds and passing dynamics of other vehicles. The air bags for street lowering are different than the air bags for 1 ton and up pickup/over the road truck towing.
A good weight distributing hitch would be a big plus with sway control.
The new SUV tow ratings are over stated in my opinion. Sure the engine and drive train can pull that load but anytime the trailer gets to be 2 times the weight of the towing vehicle you are going to have the tail wagging the dog.
This is just my opinion and take it or leave it but remember lets be safe out there and keep these old trucks on the road.