Rally Dash Wiring Harness Questions

About that 3 wire connector and lamp with blue wires. I never did find that in these 71 model diagrams. 72 model diagrams might identify that as seat belt warning or other. I know the 73 model had a added seat belt lamp poked into the inst' panel separate from the printed board. I have the 73 model diagrams on a cd here somewhere but that might add more confusion.
I got to thinking about how their engineers repeatedly added onto the blue run wire in the engine bay. Maybe the 20awg DBL you have in this 72 harness can run the mechanical limiter in the rally panel. I would be replacing the mechanical limiter with a solid state regulator and converting the amp gauge to a volts gauge anyway. My mentioning that stuff probably just further complicates things for you. Soooo, get it sorted and working first. Modify as required later on. Good luck with it