On the attached solenoid diagram, the location of that insulator is the red line. The relevant ignition ground contacts are circled in red.
I removed the rivets, and cleaned away all the old insulator material. I took some measurements of the hole pattern, and estimated the insulator thickness at less than 1/8". I then 3D-modeled a new insulator, and 3D-printed a new one in a flexible rubber-like material that is petroleum- and chemical-resistant. I installed the new insulator with some small rivets, and reassembled and reinstalled the solenoid.
Success!
The replacement plunger insulator works perfectly. The overdrive system kicks in and out as intended. Last night, I gave the wife and one daughter their first lesson with the overdrive. I guess a family that shifts together sticks together.
-Kevin
This is what happens when you live with a house-full of women, the wife and daughters name all the cars: 1960 Impala - "Frankie" (Frank Sinatra) 1961 Apache - " 'Mater Jr." (wrecker) 1965 Corvair Monza Convertible 1967 C20 "Ol' Blue" (hidden in a log cabin for 30 years) 1972 SuperBeetle Convertible - "Juliet" 1976 SuperBeetle Convertible - "Olaf" 1988 Alfa Romeo Spider Veloce - "Romeo"
