Forget the air bags- - - -and the Panhard bar. Just install spring shackles a couple of inches longer. Flatter U bolt plates are a good idea. You can also fabricate a square tubing crossmember behind the axle to serve as an upper mounting point for shock absorbers. Lower shock mounts can be welded to the axle tubes just inboard of the springs, or clamp-on mounts for a Winters or Halibrand quick change rear axle tube for a dirt track car can be fitted to your housing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!