Headlamp H4-Ceramic-Socket with heavier wire

With the rear exit on the connector, consider 14 ga GXL or Marine wire. That will provide a smaller bend radius and still have plenty of capacity. Unless of course you are going way overwattage. Then run the calcs.

I already have about 1200 feet of assorted wires that I used to rewire the car. I am not sure if I will use the 14 or 12 gauge. I am leaning towards the 14 gauge