Hi Nick,
Another thought came to mind. When I was planning the CIS to ITB EFI conversion on my car, I initially thought about combining the existing wiring with the EFI wiring into a single engine harness. I later decided against a single harness and decided to keep 2 separate harnesses. I did so because I didn't want to disturb / replace the 14 pin connector for the stock engine wiring harness - if I truly made 1 engine wiring harness then I would need all of the wires EFI and stock to connect/disconnect through preferably through 1 connector (I could use 2 connectors but that in my opinion would not look good/professional).
The key point for me was how could I best wire the EFI so the whole system (engine / transmission) would remain serviceable without having to disturb my EFI wiring connections to either the EFI power panel or the EFI connector blocks. So I decided against combining stock with EFI wiring. That serviceablity issue also drove me to install weather tight connectors on the TPS and the O2 sensor interface unit (14Point7) cable.
My modified stock engine/transmission wiring harness:
EFI wiring 1 (EFI 12V switched power, ECT sensor, O2 sensor interface cable, distributor Pertronix signal, distributor Pertronix 12V power, MSD ignition coil + & -):
EFI wiring 2 (Injector connectors bank1, TPS, Injector connectors bank2):
Hope this is clear / helpful.