Headlight Wiring Question...

[terd ferguson]

I've got a '63 C-10. I am changing the factory '63 grill and headlights for a '60 GMC grill with four headlights. The GMC headlight harness was cut where it breaks down into two wires. The factory '63 headlight harness is still intact.

So I need to cut and splice the original harness into the GMC harness. My question is, (with two wires on the original and two wires on the GMC) how do I know which wire on the chevy harness goes where on the GMC harness? They are two different styles of wire. The GMC wires are wrapped in fabric and are two different sizes. The wires on the factory chevy harness are more modern wires both the same size.

Thanks in advance for any and all help and/or tips. And thanks for this great forum.