50 year old wiring is an invitation for failure or worst case a fire. Its a safety concern.

I rewired my '64 Polara with a 20 circuit aftermarket kit because I don't have the kind of money it takes to use a reproduction harness. Aftermarket kits are all high quality and you learn a lot about how your 50 year old electrical system works if you do it that way. That said, if you don't have the ability or you're doing a concourse restoration, then an expensive reproduction harness would be the way to go.