Does anyone know what year Ford began using advanced gasket/seal materials? Cork was the preferred valve cover gasket until ____? I remember using an advanced Felpro head gasket in the mid-70s.

Not sure about the year but I've recently been buying gaskets to reseal my '64 430 and all I'm finding is cork and paper, mostly from Fel-Pro and Mahle. I did find a boutique gasket maker in Cali called Best Gasket though. I have some of their products on the way including a neoprene rear main seal so I'll be able to see how their quality compares to the big names soon.