spitfire header gasket question

I'm looking to replace the original thick as hell white paper(asbestos? fiberglass?) gaskets that shipped with the old Harold Johnson headers. Anybody know? I wish I'd read the name printed on them before throwing them out. They didn't leak and survived multiple teardowns over the years. They were the small rectangular port 273/318 style.

This is to fit spitfires onto speedmaster heads.

Any info appreciated!!

If you don’t find out what you asked, Remflex gaskets are the best you can get for hedders.

Here’s some reviews on them, and I agree with the 5 star rating 100%.
https://www.google.com/search?q=rem...AEA&sclient=mobile-gws-wiz-hp#fpstate=reviews