Answers:

4.  a.  The prototype AN/FPS-35 search radar set, produced by Sperry Gyroscope, was installed at Thomasville AFS, AL (TM-197 / Z-197), home to the 698th Radar Squadron.  Unlike the prototype AN/FPS-24, this prototype radar set was installed in a standard “fortress-like” concrete tower.  This radar operated until Thomasville AFS closed in Dec 1969.

 b.  The first production model of the AN/FPS-35 was installed at Montauk AFS, LI, NY (P-45 / Z-45), home to the 773rd Radar Squadron.  The next two were installed at Benton AFS, PA (P-30 / Z-30), home to the 648th Radar Squadron; and Manassas AFS, VA (P-55 / Z-55), home to the 647th Radar Squadron.

 c.  The last operational AN/FPS-35 also was the one at Montauk AFS, decommissioned 31 January 1981.  The radar equipment was abandoned in place, and most of it -- including the 70-ton antenna -- is still there today.  [A proposal has been made for the tower and antenna to be preserved as a static monument dedicated to all who served at US Air Force AC&W and SAGE radar sites.]