Quick ? about the H4 headlight upgrade - ground circuit.

I build relay harnesses for headlights. I use the original headlight circuits to fire each relay. Some feel the original wiring is good and acceptable. I think it's undersized garbage, plenty of voltage drop and provides poor performance. Ask any of the people that have installed a kit whether the original stuff is good.

If you are putting new headlight sockets in, I would not use any of the original ground circuit. Make a fresh set and ground them to the yoke or back to the point where your secondary ground line runs from battery to yoke. The grounds tend to link in series in an original harness. Continue to run that ground circuit for your markers/turns/etc and run dedicated grounds for your headlights. No harm in pulling the grounds for your headlights out of the system as long as the ground lines running into the original headlight sockets remain unaltered.