In trying to remove my spedometer for rebuilding, I am encountering trouble from the outset. The service manual says first to remove the headlight switch, which it describes as having a switch shaft retainer under the dash that allows the headlight knob and shaft assembly to be removed from the switch body.
When I release the button on the switch shaft retainer, the shaft assembly slides out about two inches past the "ON" position and stops, it will not come all the way out even with considerable force. It seems I am missing something that my shop manual is not telling me. Any suggestions?

May be due to old age. I would give the retainer side of the switch a shot of WD40 and let it soak. Then turn the knob while pulling out.

Are you pulling the switch to the full on position before pushing the button on the switch?

It is probably very similar to this one on the Corvair


You need to pull it out to the headlight position before pushing this button. That way the little notch you see here on the shaft is at the point where the catch can release. When you put it back in, you may have to twist a few times right or left for it to seat again.

The WD-40 did the trick, after spraying it and letting it sit overnight. Being back on the road with a quiet spedometer is so much nicer!