The remote mirror control cable need to come thru an opening in the door sheet metal. If you dry fit the door panel you will see where the hole in the panel needs to be, and there should be a knock-out on the inner side. The 65 installation uses two nut-clips, the 66 installation uses two holes drilled into the door sheet metal. Cover the area where you think the hole in the door panel will be cut with masking tape and make some marks with a pencil of the control bezel: center; upper and lower edges; front and rear edges. Cover the hole in the sheet metal with more masking tape, dry fit the panel (use 4 panel clips), punch a hole with a sharp awl or ice pick in the center of the panel to see where how the two match up and adjust your center. The rest should be straight forward.
Jim