anything could have been installed on it since 1972?

best to open it and see what you have.

then check heads for the steam holes that can get blocked by gasket.

Do these heads have the small peanut spark plug?

not sure if #346 heads had the extra cooling ports/peanut 5/8 plug

I have a set of #452 with the extra cooling ports around the plug/peanut 5/8 hex off a 78 MH 440

I also have a set of #452 regular head with a 13/16 hex plug.

my #346 set is a plane old set of BB heads with a 13/16 plug

I used the fel-pro HP head gasket when I swapped the peanut heads off for the car #452 heads. (IIRC FP 1009)