The eleven Gs400x 1977 (b) Usa (e03) Cylinder Head Cover component parts are all listed in this schematic.
Parts such as the Cylinder Head Cover: Separator,oil Breather, Cover,breather, Gasket (mca), 01550-06307 are included in the Gs400x 1977 (b) Usa (e03) Cylinder Head Cover parts fiche.
The most reasonably priced component used on the Gs400x 1977 (b) Usa (e03) Cylinder Head Cover is the 01550-06257.