Years ago I looked at most if not all the various 60's and some 70's head gaskets for small & big blocks & even slants. As stated the early ones were all stamped steel (one exception below) but at some time in the 70's they did go with composites & you have to be wary of superseded part #s. There were some part # changes where they slightly changed water passage hole sizes but nothing significant. The thing they did do was have gasket bores that more closely matched the actual engine bore. Later when mopar performance put out their replacement gaskets they were one size fits all with a huge bore. You will lose a small amount of compression with those on the smaller bore engines.
The one exception to the rule was the aluminum slant, they actually used a copper shim gasket! I found one of those for a local guy, believe it was a NORS Fel Pro, very hard to find. The aluminum slant is a really bizarre motor, the block is actually die stamped rather than cast. Just imagine the size of the tooling to do that!
Believe the factory used some type of material (very lightly) as a sealant originally. it appears to be a sort of brown color, not the copper stuff that's commonly used now. The factory block/ head surface finish is very smooth & you have to duplicate that if you want to ensure no leaks.