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You're missing the actual relay part of it. The Feds rescinded the requirement to have the interlock early in the '75 model year. Many dealers disabled them upon customer request. Is your VIN before #402257? Or after #409190? Cars before #2257 had the system intact and operational; after that number and up to #9190 the system was installed but not connected; and after that, the system wasn't installed, though I don't know if that means the dash harness was changed to eliminate the connectors.
I also don't know about the red bar, maybe it's a bridge that stops the seat belt buzzer from activating? Is it metallic with bare ends that would electrically connect the two end wires?
Here are a couple eBay pics of the relay, you can see how your connector fits it.
I believe you are correct, on page 6 of the owners manual it clearly states there is NOT a starter interlock on my car, likely a remnant harness with a jumper (Red Conductor) to complete the circuit.
I am sure that my car was delivered sans relay. I bet in 1976 that harness was eliminated.
