How do you change a heater core on a 1983 chevy truck?

SOURCE: how to change heater core in 92 chevy pick up

unfortunately the fastest easiest way is usualy to remove the entire dash and its about a 2 day job

SOURCE: heater core

http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800bfedd

SOURCE: what is the process to putting in heater core in

If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired.
Heater Housing

• The heater housing is usually under the dash and must be removed to gain access to the heater core.
• Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.

• Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
• Remove the heater coolant hoses.
• Remove the cable and/or vacuum control lines (if equipped).
• Remove the heater core securing brackets and/or clamps.
• Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
• To reinstall the heater core, reverse the removal steps.