Parts such as the Crankcase: Cap,oil Gallery, Bolt, O Ring(d:1.9,id:18.8), Washer are included in the Gs1000e 1979 (n) General Export (e01) Crankcase parts fiche.
On this parts fiche the Bolt 6x35 is the most specified component.
Check out any of the thirty-nine Crankcase components enlisted.