Dash lights

If the lights are constantly dim the problem is in the system between headllight switch and bulb. If the light dim at idle and blare up nicely at higher rpm the problem is in the entire cars electrical supply and showing itself in the lights. That will lead you to the altenater, regulator, and wiring through the bulkhead, amp gauge, chassis grounds, etc...
You likely have a mere 36 amp altenater. Not much compaired to todays high amp units but it was sufficient when the car and parts were all new. To upgrade to a higher amp isolated field unit and solid state regulator is a common solutition. This is really just override the problem. Whatever it is that contains resistance today will only get hotter and surely melt down and show itself eventually. Good luck