what do you call these parts
The lower bushings varied a lot depending on model year, options, etc. Some had actual bearings, some had plastic bushings, some just had what basically amounts to a plastic seal.
The bearing or bushing style ones are about $80 to replace.
But an ER16 flange bearing fits in there pretty well too. Here's how I did mine...
http://www.forabodiesonly.com/mopar/showthread.php?t=228103