I am getting ready to install a RE 3.5 but the kit is pieced together. The springs I am buying new but I bought a set of used RE upper and lower control arms, discos and HD track bar from a friend. The parts are in very good shape. I was wondering if installing the upper control arms would be needed for a 3.5 lift. He through them in with everything else becuase he now has a long arm. Also, I will be ordering new U bolts and axle shims, steel not aluminum. Would I need anything else. I already have a 3in that I have had for 4 yrs now and it is starting to sag.