Need to stiffen my rear 68 dart suspension

My Duster handled like it was on rails lowered by flipping the front spring hangars with SS springs and a 7/8" rear bar. Very stiff, neutral handler like what you are looking for. Only problem was it bottomed out too easily. I have since "un"-flipped the spring hangars due to spring sag, bringing it back to a stockish ride height, instead of the lower-in-back look.