As to the safety switch. I think it was only used on 76 models.

Its purpose was to shut off the fuel in case of an accident and the motor was shut down but the key still on.

It was not safe enough and they put circuitry into the fuel pump relay that used engine rpm for the same purpose.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician