In addition to that. 993 balljoint will have 2mm wobble sitting on 964 knurled bolt:
in details described in beginning of this thread:
http://forums.pelicanparts.com/porsche-964-993-technical-forum/693615-random-notes-964-993-suspension.html#post6903464
You may
1. bore out opening in 964 a-arm and press in 993 part
2. Machine 1mm wide washer to go between 964 knurled bolt & 993 ball joint.