It is most likely the thrust rod bushings. I experienced the same thing. I replaced the entire lower control arm (they come with new bushings) and it took care of the problem. I still had some shimmy when breaking but getting the front and rear brake rotors turned took care of that (they were slightly warped).I am experiencing he shimmying and wobbling when breaking at about 50-60mph, but I am also experieing the same thin when just driving at about 65mph.
Sears told me it may be tie rods and possibly bearings.