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i believe it was a Cole Hersee Rotary switch because i went to 12vdc w/ the 292 and alternator. many of my electrical is from Cole Hersee. their stuff is good quality and one had to be creative when fitting a newer designed anything in our old trucks. it turned out nice.
most of the chevy supply houses that offer us folks have cheap switches. i had a $44 H/L new vendor switch from a vendor that LITERALLY FELL APART IN MY HANDS as i installed it into my 51. so i wrote it up for all of us bolters and simply rebuilt my stock switch. it was made in china and failed.
http://www.elecdirect.com/catalog/cole-hersee-switches/cole-hersee-rotary-headlamp-switchesthe reason you see the stock C choke turn switch is because i ground down and glued the C onto the black cole hersee knob so it appears stock.
i left the cole hersee knobs as stock on the wiper and safety START / FOG switch on the left side of the wheel