Welcome aboard. Sorry for the delayed salutations, busy with bachelor life and school.
If you need individual wires to splice into or repair an OE wiring harness, I have all the wiring you need. Grey tape is available at your local hardware store for the close to OE look.
If you are looking for an OE Datsun 320 wiring harness, sorry I do not have an extra. Your best bet is to go with a generic 6 fuse wiring harness. Might be available locally (?) or go to google/eBay and see what comes up. I've priced one for my parts 320 and they run ~$200 (I think) for a complete front, engine, dash, and back harness.
So I would definitely compare the price of an OE harness of unknown condition to a brand new generic one before giving up your debit/credit card #.
Again, welcome to the NiCo 320 Forum