All 911s from 1970-1989, excepting those 70-73 cars that were equipped with the spring struts, used the same 911.341.018.00 upper strut mount.
Removal of the shock absorber is the same for all of them, be it Boge, Koni, or Bilstein, just like Greg described. Take off the top lock nut, push the shock absorber shaft thru the mount and the upper part of the strut assy. is now disconnected without disturbing alignment settings held by the upper strut mount.
The type of strut insert will determine how to get the insert out of the strut body.
Boge inserts (some inserts are integral units and have the guts & oil right inside the tube) are held into the strut tube by a collar nut @ the top of the tube.
Bilstein are held by the collar nut and a tension pin @ the bottom of the strut.
I don't know how Koni are fastened to the strut tube........
