Here's the 2 pictures of the switch from the 1948-51 Chevy Truck Shop Manual that includes the one Otto mentioned.

Should help you locate the push pin to release the shaft. On the 12V use question, yes it'll work. wink
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~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)