Turn signal harmonica plug wiring different - 1977

[bigoilman]

In the midst of replacing my turn signal switch and realized that the original has an additional pink/blk and black that the replacement part doesn't have. Looked through my schematics and don't see it there either? What do they operate? Do I need to add them to the new plug? The switch seems to have provisions for them.

Only thing I've found online is for a similar vintage Corvette and those went to the "key alarm" whatever that is. (Edit: found the answer to that, see pic). I guess my truck got that feature (it was a fairly loaded Silverado with Cruise Control) Wires are in positions "E" and "F" on the harmonica connector.

1977 C30 Dually Silverado

[hatzie]

The 1977 and prior CK pickup harmonica plugs will not mate with the 78 & later cab harnesses.
There were a bunch of wiring changes between 73 & 77. I would download the 1977 wiring diagrams and look through them.

The seatbelt buzzer was used as the headlamps (parking lamps on, ignition key not present, door open) and key in ignition with door open warning as well.