The fixed side of the leaf spring is rubber (actually a metal bushing encased in rubber with an outer metal jacket). The shackle side is all metal so you have to grease them constantly.
Part numbers:
Rubber Bushing (fixed pivot of leaf spring): 55045-07200
Metal Bushing: 55046-00902
Front and Rear springs use the same. Both bushings are 5/8" i.d.