I wanted to change gears one time and found it easier and cheaper to buy another rig similar to mine, with the right gears, that was wrecked. I paid $800. for the wreck, pulled and swapped out both complete axles, took the best part of a day with a buddy doing most of the brain work, and i lifted a few other parts i wanted. I then sold my old axles and what was left of the wreck for,... you guessed it, $800.
I put Firestone air bags on the rear of my 3/4 ton truck last summer. At 50 pounds pressure, you can go to 100, they lifted my back end 3-4". Love them!! Cost? $300.
Just some ideas,
Joey