I've decided to buy an older 06-09 megacab 3500 dually instead of a newer one specifically so I will have the money for all the upgrades I want. Along with doing a longbed conversion, I've been searching for an adjustable suspension lift kit that will allow me to drive with a nice ~4-6" lift that functions better than stock but also lower to stock height in order to tow a heavy 40ft. 5th wheel while also having better than stock functionality. I can't seem to find a system like that and am starting to wonder if it even exists. With airbag technology nowadays this surprised me. Any thoughts? recommendations? Currently I'm just thinking of going with a leveling kit for the front and the airlift 5000 for the rear. But i would really like to be able to lift it.