Theres a wiring harness on ebay I want and it says its prewired which is what I want. How would you get the 3 way switch in the slot? If its wired then the wires would have to rest outside the guitar.
to get the 3 way into the horn of the guitar they may require you to do a little soldering yourself... i'm not sure. i'd send them a message about the harness you want to buy and ask them how to install. any company on ebay that's worth buying from will be friendly and helpful, it's a pretty decent community on ebay.