I highly doubt that there are performance shocks designed for the 73+ b/r body available. Last I recall you'll need shocks for a late 60s GM A body (Tom Quad did this on his St. Regis). Easiest way to upgrade the handling is to look for someone parting a 79 Chrysler 300 or Magnum GT and grabbing the torsion bars and sway bars from them. The rear away bar was available also on toe package cars. The other thing is to eliminate the iso-clamp system on the rear axle and replace the k frame and torsion bar crossmember bushings with Firm Feel's aluminum ones. That's a one and done upgrade, the poly bushings available are better than nothing and I would only recommend them if you don't plan on keeping the car.

I built the 300 in the beginning of this video:
http://youtu.be/LHj8QGpxCL4