If you already know you'll be working on the floors,then by all means take the body off the frame,now you can work on both sides to repair the floors. Take out your tape measure and notepad and measure and map out frame width wheelbase,body mount locations. Now go visit our old buddy,Gary's u-pull it,and see if there isn't a much later model frame you can stick under that thing. Swapping frames isn't rocket science,and it immediately brings you up to date on braking and handling. Take another look at air suspension,it works good, and rides very nice at almost any hieght you choose. Hank