I went through my entire stock harness by removing the tape or wrapping and inspecting each wire for it's entire length. It sounds like a big deal but it's not. If you have the factory wiring diagram to follow that really helps too. When reinstalling it, be thoughtful of what upgrades you want to do, like relays and put it together carefully. I successfully removed all the wiring related to the key interlock system on my 74, added headlight relays, redid the wire from the alternator to the battery so it would avoid the firewall and amp meter (replaced with a volt meter). I modified a bunch of other stuff too, but my point is, usually the stock harness is a great starting point for a custom harness without the hassle of starting from scratch.
Learn how to solder, buy some Packard 56 crimp on ends and a good crimping tool to install them and a whole bunch of heat shrink. Don't be scared of automotive wiring, just think about it and don't cut corners. It's not the black art some think it is.
Cley