The most reasonably priced component used on the Gs750ec 1978 (c) Usa (e03) Fuel Cock is the Bolt(6x20).
Parts such as the Fuel Cock: Bolt(6x20), Gasket (nas), V Seal,fuel Cock, Gasket, Fuel Cock (nas) are included in the Gs750ec 1978 (c) Usa (e03) Fuel Cock parts fiche.
On this parts fiche the Bolt(6x20) is the most specified component.