I was thumbing through my Eckler's catalog and noticed a replacement headlight switch knob and shaft. http://www.lategreatchevy.com/produc...dept%5Fid=1681
Interestingly, it seems the back end of the shaft looks like it has a channel for a clip in it. I bet there is a clip on the back side that needs to be removed for the shaft to come out. I will check it when I get a chance.
Nope, that is not quite it. I looked again at my replacement switch, and see there is a button on the underside that seems to serve as the 'clip' to the shaft. I can see the 'clip' move inside the shaft area when I press the button. The button looks like a rivet with a spring on it. Give it a push and it should release the knob and shaft.