On my 67 the firewall connector is for the convertible top motor. Also could be for power windows or other power options. ( I think it is a circuit braker)
Correct, it is a circuit breaker, factory installed for power options such as power vert top, windows and maybe factory A/C cars, not sure about that though.
RockAuto calls it a stud circuit breaker, 30 amps.
If you do use that connection for additional power accessories, make sure you're not going to run both or more at the same time.
