Jinglebob,
When I owned cool cars (I no longer do
), I always joined the marque clubs. They provided great advice on care, maintenance and restoration. I'm not a member of the GTO Association of America, but they look like a pretty active group. I'll bet they will help you with parts acquisition and technical advice. In case you're not a member, here's their website:
About the GTOAA >> GTO Association of America