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T-Bucket "Quote" [Well that depends on what is wrong. How do you know you need a core and a switch. The two would be for unrelated problems]
It the process of replacing the interior firewall pad, I noticed the heater switch had deteriorated, literaly fell apart (appears to be original switch).
As far as the core, I was advised that it would be a good idea to replace it while I had the heater unit out.
If there are other 40 years old parts that could possibly be replaced while the heater unit is out, it would seem to be a good idea to replace them, especially if they are inexpensive parts...