I recently replaced the non-working pins on 2 of my trucks. On some trucks, I think there is a small pad that bumps out on the a-pillar that they go into. I would need to check as the holes were already there - just the pins had gone bad and were no longer grounding.
They should tie into the 'courtesy light' /dome light harness under the dash. You can add the CL harness if you don't have it.
http://67-72chevytrucks.com/vboard/s...d.php?t=618187
Pin location thread - I need to check mine and see where they are compared to the hinges.