A sample from the products for the Oil Pump include: Ring-o,oil Filter, Gasket,solenoid (nas), Washer,13.2x20x0.5, Bolt-socket,6x25.
On this parts fiche the Bolt-flanged,6x22 is the most specified component.
The component with the lowest price in the OIL PUMP schematic is the Bolt-socket,6x20.