Found out something on the mirror cable lengths

The clip has a tab on it. there is a slot on the top of the hole in the door. The clip has a flat spot so it only goes on the control one way one way. When the tab goes in the slot it assures that when you move the little lever up the mirror goes up. Down is down and so forth. I have never seen these clips forsale anywhere. The nut most often seen is for 73 models when the control is through the door panel. It holds the control in place until the door panel is installed. The chrome facia nut on a 73-76 is for appearance trim to cover the hole in the panel.