The following photos exhibit the comparison between a stock Eagle strut rod and a Specialty Products adjustable strut rod for a 1965 Mustang. The Eagle strut rod is on the left in those photos.
The bottom line is that they are incompatible. This product will not replace an Eagle strut rod. HOWEVER, I am beginning to believe that Mustang strut rod bushings are compatible with the Eagle. I must do more testing in order to confirm.
It is my hope that you find this useful. Let me know if you have any questions.