Dim Lights

Hey Charger 426, Had,same issue,
1. did you have car dissassembled for repaint/restoration? If so, ground points may be covered with paint .You need bare metal for a good grounding point.
2. MoparMat2000's point is valid. Great way to eliminate this problem prone factory harness problem
3. Redfish is also correct. The wiring works fine when re assembled to factory specs with good clean connections and connectors.
4. Start with the simple stuff first, replace each bulb,especially the 1157's as shorted filiments can no end of electrical havoc.
5.Don't assume anything is functioning correctly even if it is a new component. Even new or re-manufactured components can be faulty.
6. Alternator and wiring been replaced/new?
7. Ignition new/replaced ?
8.You mentioned wiring modified for an aftermarket stereo. Like I said before, look for the simple ,obvious stuff first. Check out the modifications to the wiring harness used to install the aftermarket stereo and return them to the factory configuration.
9. Start the car, and remove the accessory fuse .

I don't profess to be an expert but I do have 23 yrs experience in the electrical/electronics field as a technician.

I don't have a lot of details to work with here so I hope this helps some.

Good luck with it.