I heard back from the builder. He said they used an insulated comb which is for the 3 prong NSS. He did note that it will work with a 66-69 single prong switch, but not other single prong switches.
So the one you bought must be for another application - possibly pushbutton Chrysler.
Ask A&A if they have one for '67. That's the simplest route.
Or post here in the wanted section.
or look up the p/n for 67 and search for that