removel of headlight switch

There is a button straight on the bottom of the switch unit behind the dash that you need to press up on to release the stem of the knob. Once you pull the knob out, you can unscrew the bezel from the front and pull the switch out from the back. Note that this is really tight -- on a 68 that bottom dash pad might make it even tighter. Also check your tail lamp sockets for corrosion. And the pins on the lighting switch, for that matter.