Whoa! Ooops! Correction!
This is the switch used on '47-'53 trucks. The '54 GMC (and "'55 1st series" GMC)had a toggle on the dash above the radio and to the right of the guage cluster, in an odd spot.
I am unsure about how Chevy truck heater switches were set up on '55 1s series. I know that it is a two speed (three position w/off) switch because I have an original '55 1st series Chevy Truck data book, but as far as the type of switch, I am now uncertain.
