Parts such as the Oil Pump - Belt: Belt, O-ring (6g8), Nut (6g8), Washer, Plain (646) are included in the Ft9.9 (e/er)d 1990 Oil Pump - Belt parts fiche.
In this schematic the "Bolt, Hexagon(663)" is used most often.
The Oil Pump - Belt assembly is constructed from several parts from which the Shaft, Cam is the most expensive.