For what it's worth, I was working at LAX for TWA as an aircraft mechanic and one of my peers had a '67 GT500.
He happened to live in an apartment in Playa Del Rey and one morning, when he was emptying his trash into the
dumpster, he saw sheets of foil paper. Upon a closer look, they were sheets of the foil inserts, for a '67 GT350.
However, they had been printed crooked and were unusable. So, he took a sheet for his collection and showed it
to us. From that, it could be assumed, the producers of the '67 GT350/500 inserts, were somewhere in the local
area, perhaps close to Lax.
Doug C.