The long shackles are the biggest part of your problem. They do not help Mopars due to the asymmetrical nature of our leaf springs (roughly 2/3 of the length behind the axle with the greater spring rate forward of the axle).
For a cheap ride height adjustment there are coil-over helper spring kits (you keep the leaf springs and these just go over the shocks to help). I have used them on my Barracuda and my son's Dart.
