You need to install the thermostat, the thermostat housing, and gasket, RTV sealer (GM P/N 1052366 or the equivalent) to the thermostat housing bolt threads, then install the thermostat housing bolts, the radiator hose to the thermostat housing, and the air cleaner and duct assembly, fill the cooling system and inspect the cooling system for leaks. Repair as necessary.
By BobGM Specialist
01/11/2022