I have a somewhat similar problem on my '81.
When I turn on the headlights, the dash and rear lights will take a few seconds to come on. Maybe 5-10 seconds, but they still come on. I know there is an issue, just haven't had time to look into it.
Can you explain what you mean by headlight switch? Are you talking about the turning knob on the stalk itself or is it something else? Should I try and get a stalk from another car?