I'm not an expert on heaters, but I see yours has a GM emblem on it. There were many styles & years of heaters that were used in these old work trucks. Here are photos of
1952 Heaters . Notice there was a Fresh Air and a Re-Circulating version. Any heater switch could have been used. Any parts house of the day sold many styles. The switch was usually mounted under the lip of the dash close to the driver.
There is a reconditioned heater on
Ebay (not mine).
Harold
