Flickering tail lights

[Nima]

Hey:
First of all thanks to whoever wrote me back about my carb problem. It is in rsolving process, I let you know as soon as I am done.
Now, at the same time I am working on the electrical system. My tail lights flicker and fade gradually when the engine running. Is it charging system and/or ground issue? My truck has messed up wiring, but at this point, I can't afford to buy wiring harnesses. I appreciate any input.
Thanks.
By the way, I am still working on posting pictures!