How do you replace heater core in 86' Chevy g20 van with no glove box?

To replace the heater core in an '86 Chevy G20 van without a glove box, start by disconnecting the battery and draining the coolant. Remove the dashboard and the instrument panel to access the heater core housing, typically located behind the dashboard on the passenger side. Disconnect the hoses from the heater core and unbolt it from the housing. Replace it with the new core, reassemble everything, refill the coolant, and reconnect the battery.