Replace heater core in 1969 Buick Electra?

To replace the heater core in a 1969 Buick Electra, first disconnect the battery and drain the cooling system. Remove the dashboard to access the heater box, then disconnect the hoses and unbolt the heater core from the housing. Install the new heater core, reassemble the heater box and dashboard, and reconnect the hoses and battery before refilling the cooling system and checking for leaks. Be sure to follow a service manual for specific details and torque specifications.