PROBLEM SOLVED! It was the switch all along. Spent the money on an NOS switch, popped it in, and it now works perfectly. Both 74 Dusters that I own had the identical failure mode. It appears that water got into both switches somehow. They corroded and failed. And it was never that good of a switch in the first place. Definitely not designed to last 43 years. Anyhow, thanks for all the assistance to my fellow Moaprites!