The most reasonably priced component used on the Gs400x 1977 (b) Usa (e03) Rear Hub is the 01500-06257.
This schematic depicts all components used in the Gs400x 1977 (b) Usa (e03) Rear Hub partslist.
A sample from the products for the Rear Hub include: Panel,rear Hub, Spring,brake Shoe, Lever,rear Brake Cam, Oil Seal.
