[Westmus]

The problems may relate to that they aren't "real" Bilsteins, since Bilstein don't officially sell shocks for old Mustangs. They are RCD shocks based on Bilsteins, so those top mountings are probably something RCD put on the shocks. It kind of also fit with that other mounting parts also don't seem to be designed exactly for the Mustang and the torque specs are wrong.

 

[Westmus]

Who's the vendor?

It's Bilstein manufactured shocks, but modified and sold by RCD: http://racecardynamics.com/ That's also why the shocks have an big red RCD logo above the Bilstein name on the sticker. Think of it as similar to an Shelby. Shelby bought an stock Mustang from Ford and modified it to become an GT350.