1963 Valiant Wagon "Candy girl"

I used these. No problems. My understanding is they are a little thinner than Remflex. A little over $50 for both gaskets including shipping from AU.
HP Premium Graphite Manifold Hot Box Gasket : suit Slant 6

All the above gasket posts are good information but...., PV is using 3 into 2 Headers and a non stock intake so this has nothing to do with her build.

If you are 100% stock IRON exhaust and intakes then you MUST follow the tightening steps or it will cause a stress point in the exhaust manifold.

My last /6 we brazed the exhaust pocket shut with 11 gauge tin and ground the intake mating area down so they did not touch.