Problems with lights

[67ChevNut]

Having issues with my taillights, etc. My taillights don't work unless I turn on the emergency flashers. The emergency flashers work ok if my headlight switch is off, but if I turn it on, they stop and my steady taillights work. My brake lights don't work, and my gauge cluster lights don't work either. The reverse lights don't work. My headlights work and my turn signals work too, only front passenger turn signal doesn't work. My headlight switch is new, my rear taillight wiring harness is also new, the flasher is new, and as far as I can see, the fuses are good too.

Where do I begin to fix this problem? What may be the problem(s)?

Sure appreciate any input, thank you.