I have added watts links setups to two modern Mustangs, a 2006 and a 2009, to replace the stock panhard bars. IMO, it made a tremendous difference in handling, about as close as you can get to feeling like independent rear suspension with a solid rear axle. I have no idea how they would work with an older Mopar.

Also, the setups I installed were kits engineered specifically for those Mustangs. It probably would take a lot of auto engineering knowledge (at least at lot more than I have) to design a setup from scratch.