Steering coupler basic questions

When reassembling this, The notch on the coupler just left of the roll pin shown in your first pic is also an index mark. is supposed to line up with the index mark on the shaft. This is because the steering box, the coupling, and the steering wheel all have master splines and only go on one way. If you put the coupling back together with the index mark opposite or 180° out from the shaft your steering wheel will be clocked upside down when centered. You cannot pull the steering wheel and rotate it 180° and reinstall it since it also has that master spline too.