Pads? The "pads" referenced above are where the leaf spring fits in its mounting clamp to the axle. Might be better to find some in polyurethane, but they'll cost a little more.
There were two types of spring inter-leaf pads that Chrysler used. One was the wax-coated version with a plastic dowel that snapped into the spring leaf's hole at the rear of the leaf. With time and use, they'll deteriorate and need replacement. Just pry the leaves apart and install them carefully.
The other type was a zinc-coated thing spacer for the HD springs, from what I understand. Main thing was noise attenuation as the springs flexed against each other.
In some cases, removing the rear leaf clamps can get a better launch in drag racing situations. Upon initial acceleration, the rear leaves will physically separate from the torque reaction. Interesting to watch! But I also suspect they need to be there to help with lateral forces during cornering maneuvers.
CBODY67