[Bradical]

1.) If it were the speed ref sensors the car would not be able to start because the fuel injection would not work.
2.) The O2 sensor wont stop the gauges from moving.

I hope someone else can offer some more help- sorting out that electrical should be priority one. I believe that black connector that you didn't circle in picture #4 is supposed to be connected to the gauges. I am not familiar with the early dash assembly though.