Thermostat case Engine Water Pump Gasket. #8 on Dealer Diagram shown in the last photograph. Part is circled in red. Be sure the part you are buying is correct for your application. They may have been in storage anywhere from 1-30 years.
Engine Coolant Thermostat Housing Cap-Standard Coolant Thermostat Housing Cap
Engine Coolant Thermostat Housing Gasket-Thermostat Gasket Gates 33641
Engine Coolant Thermostat Housing Gasket-Thermostat Gasket Gates 33644
Engine Coolant Thermostat Housing Gasket-Thermostat Gasket Gates 33624
Engine Coolant Thermostat Housing Gasket-Thermostat Gasket Gates 33633
Engine Coolant Thermostat Housing Gasket-Thermostat Gasket Gates 33631