Classic/Antique Car Repair: Headlights, 1970 chevy c10, switch fuses

Question
On my 1970 Chevy C10 Pickup Truck, I have replaced the headlight switch, fuses, and put in new headlights, however, the headlights will not work, but the taillights, parking lights do.  What could be the problem with the headlights?

Answer
Well the one thing that you did not mention is the headlight dimmer switch located on the floor board by your left foot. Check to see if there is electricity getting to that switch with the headlights on, and if there is check to see if there is electricity getting out of the switch. There should be three wires to the switch, one in from the main headlight switch and one out for high beam and one out for low beam. You will need a test light or voltmeter for this test. If there is nothing coming to the switch it is 1. Headlight switch. 2. Wiring. If there is voltage getting to the switch and at least one output leg is not sending voltage out, then the dimmer switch is defective. One last thing to check is the ground wires for the headlights. The grounds could be bad. Good luck.
Brad