Fading at idle is a common issue with the early 70's mopars if the electrical system is stock. Check into ammeter bypassing and relays to eliminate that. As for bumps making the lights flicker, you have a loose connection. Where? Depends on whether it makes all the lights flicker or just the front, just the back, etc. If it's all of them, something in your switch. If it is just the front or just the rear, I'd be going over ground connections for that area. That's how I'd start, see where that takes you.
PS. The front lighting goes through the bulkhead connector, the rear has a connector in the front left kick panel. - if you didn't already know. The two ccts are separate.
