Hi Mike, for the distributor there is the screw which goes inward in indentation in the distributor shaft and action plate 408992. Others may confirm that this screw is C.415 Screw, locking Distributor through Tappet Cover which uses FN.104/L Nut, locking Screw in position, and FG.104X Washer, Spring, under Locknut. On my car, that screw is screwed into the indentation without pushing radially onto the distributor shaft. That screw locks the distributor from vertical rise when running, especially when timing adjustment is being made.
There also is a collar around the distributor (the one on the left photo with red arrow pointing towards it). This collar is distributor part 41909 Plate Assembly which is locked down by the screw shown on the right photo). This screw should be secured tight at all times. The Plate Assembly has a loosening mechanism, hidden in the photos, which has a screw that can be loosened. When that loosening mechanism is loose, the distributor can be rotated to change mechanical timing set point.
