I honestly cannot believe that the upper ball joints can be so bad that they exhibit a clunk. You would notice the steering being all over the place before they would get this bad. They normally fail by starting to squeak, not clunk. You can drive them in this squeaking mode for many miles, if you are not annoyed by it.

I'm a little confused by "castor rod bushings" as well. I don't understand this term on a W126.

I would additionally like some clarification of the "subframe bushings" on the front end of a W126. Are these bushings the ones that are used to hold the guide rod mount bracket to the frame? I presume that you changed these, Hattie, when you did the guide rod mount.