You have to consider that, when on the medium and low settings, the resistor on the back of the switch, gets really hot.
Therefore the switch probably didn't last very long and had to be replaced during the life of the truck.

One thing that they do with modern switches is they separate the switch from the resistor. Picture
The selector switch is mounted on the dash and the resistor is mounted inside the heater duck work. Picture
The fan circulates air pass the hot resistor, cooling it down.
Which may make it last longer.
Also adds a little heat to the circulating air.

I was thinking that this could be done with the older Delco or ARC-LES switches.
Use the same switch and remove the resistor on the back and mount it inside the heater box.
But then it wouldn't be stock.

FYI, this 1949 Chevrolet Truck GM Vehicle Information Kit, PDF page 49, actual page 99. Top of the page,
Accessories
Definition: Items made available at extra cost through the parts and accessories department and installed by the customer or his dealer.

So that means the customers or the dealer could have installed the accessories.


1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC