1974 was the first and only year that the federal Government mandated the seatbelt interlock system. This system required the occupants of the front seats of the car to be buckled in by the seat belts before the car would start. The front seats had sensors in them and when they sensed weight, the car would not start without the seat belts engaged. The public hated it and it was canned after one year. Part of the problem was that if you placed something even as trivial as a bag of groceries on the right side, the car wouldn't start without the belts buckled.
I once had a 74 Duster that had similar yellow wires such as yours, they went to a strange looking metal relay mounted to the left fender apron. The relay was about the size of the starter relay, but this one was different. It was part relay, part RESET switch. If the seat belt interlock was defective, the switch had a red button you'd press and it would override the system for ONE start. If the sensors under the seats were disabled and everything else was left as is, you'd have to press that reset switch EVERY time you started the car. Thanks, FEDERAL government!
Your yellow wires have shrink tubing on them, indicating that they may have been changed at some point.
In the case of my 74 Duster, UNDER the dash, on the other side of the firewall, those yellow wires ran into a plastic box. Inside the box was a computer type circuit board. This was the "brain" of the seatbelt interlock system. The box was a light blue color, about 3/4" x 4 " long. Some of the wires from it went to the steering column and into the ignition switch wiring.
Cars like ours have had multiple owners and stuff often gets switched and moved. If you do have a shop manual for your exact year and model of the car, you can verify what really goes in those terminal holes. I suspect that it is the Seatbelt thing since it is a '74 model.
