DDK - Die Deutschen Klassiker

I am doing full restoration of 911E from 1969. When I dismantled the front strut from the A arm ball joint I found a M10 bolt with a damaged thread holding it on. The shaft of the ball joint has a notch to accommodate a pin or bolt so I tried screwing in a new M10 bolt but it is not a good fit on the notch and doesn’t seem right to me. Anyone had the same problem? I would be great full for any information.

The early threaded bolt that you describe is a bad design on the 69-70 cars and can work itself loose. The later cars have a better designed strut that uses a wedge bolt. Your choices are to re-tap your existing thread and fit a larger bolt, or covert to the better wedge bolt design. I re-tapped my existing Koni strut and fitted a bigger 12.9 bolt.