Harnesses from different production dates are not compatible. People have asked for me to check the compatibility of harnesses from different productions dates. I would need to have both harnesses and spend about 10 hours looking at both harnesses. I would need to check each connector, each wire at each end and the continuity path of the wires. Now thats a headache. Anything less would be unprofessional and definitely not safe. The Datsun 240z engine bay harness is very similar on the engine side, but all the front connectors that plug into the other harnesses may not match..not to mention the wire colors and circuits. If you need a replacement harness, find your production date on the door id plate and find the harness tape that has the OE part number on it. I offer harness rebuild services.
These images are from https://www.carpartsmanual.com/datsun/Z-1969-1978/electrical/wiring
Thanks for your great effort, really appreciate all your hard work!