The headlight switch (at least the ones I have) have a bi-metallic circuit breaker mechanism. If I remember correctly it is externally accessible. You could try jumping it to see if that is the problem. My limited experience is that the reproductions are a little "testy" with the contacts of the circuit breaker strips. I cleaned and re-arched mine and haven't had a problem since. However, the truck is fused, so I don't depend on the headlight switch for overload protection in that circuit.
don
