72 Mustang Seatbelt Light Wiring

I'm repairing all the electrical in my car that was messed
up over the years, and have run into a snag with the
seatbelt warning light system. I have schematics, but
for some reson they don't show some of the circutry.

I understand whats going on in the seatbelt retractors

In the dash, the light and buzzer are connected in
parallel, but that's where I loose it. The wires from
the buzzer go to a small round connector with two
connections, (I'm missing whatever that plugs into)
then a brown wire disapears into the harness.

Without ripping the entire harness apart, I cant find
where or how it connects to the purple wire that
goes to the seatbelts or how power is applied.

Any hint's help or schematics welcome.