Over compensating for the lift by increasing the tension on the hitch is not a good solution.
My dealer recommended the option of just adding a 1 or 1.5 inch block under the leaf springs in the rear in order to bring the rear up a bit. He thought that air bags might make a rough ride.
^This would be the easiest and cheapest solution with the least affect on towing, especially if you like the lifted look. I have 2.5" lift on the front and put 1" blocks on the rear to keep the rake. It had no affect on towing. If you look at most HD trucks these days, they come from the factory with rear lift blocks.
Airbags will stiffen the suspension and can make for a rough ride when unloaded. The rubber bags are really stiff and you need to maintain a minimum of 5psi in them. The double bellow style seem to be more forgiving than the singles.
