I would just re-do the wiring. Cheaper and like you said its old wiring. On the plus side, you can make it longer and route it away from the header.
![Thumbs Up :thumbs:](https://board.marlincrawler.com/Smileys/marlin/thumbs.gif)
I had to this to mine. Well worth it. I bought a used harness, and spliced in all the original color coded wires. And I lengthened some to make it a cleaner setup.