Make your life a little easier. Instead of disconnecting wires and switching them, have a decent length wire with an alligator clip on each end. The amount of diagnosing alone you could do with that tool would just amaze you. Work smarter, not harder as they say. On the '51, battery hot from the alternator, and touch the other end to the headlight terminals on either inner fender. Verify the lights are good before assuming any of the switches are bad.
I can remember when I learned this lesson. It was on a Ferd station wagon. The last of their breed. Both low beams out. Ordered the switch, it came in and I proceeded to do battle with the steering column. Yes, late model column switch. Took me most of the evening with the newly returned lead mechanic telling me we weren't going to put in any overtime. We were averaging 3-4 hours nightly. He was back from cancer treatment and didn't have the energy to stay. So, if he went home, everyone went home! Anyway, got the switch done 30 minutes or so before end of shift. Still no low beams. Then it hit me. There is no way the driver would wait until both low beams were burned out, would he? He couldn't be that dumb! He was. I learned. Still got the job done by shift end but that was some unnecessary labor and parts thrown at it!!
Do the simple stuff first.
