Electrical problems 73 duster

There are two positions on your key switch:
Start 1 = Normal running
Start 2 = Engages the starter and bypasses the ballast resistor.

You perhaps damage the key Switch or somehow lost power somewhere
in the column (pinched wire in loom)
Possibly but less likely is that you somehow damaged the ballast resistor itself
(Maybe left key switch on overnight).

However, I suck as an electrician and have the blown fuses to prove it in the tool box!