A sample from the products for the Rear Case include: O-ring,21.5x3.2, Gasket,rear Case (nas), Plate,prim Brg Se, Oil Seal,28x48x9.
Of all the components that make up this Rear Case the Bolt,flange,6x16 has the lowest price.
In this schematic the "Bolt,flange,cap,8" is used most often.