Attach the heater hoses. On this install, the original heater valve was removed. The valve is a common leak and failure point, though bypassing it does send warm coolant to the heater core constantly. The flaps inside the HVAC box are relied upon to keep that warm air from entering the cab when the heater is not turned on. Fill the system with coolant and check for leaks. Better to find leaks now than after you have reinstalled the dash.