First welcome to the site. Hope you find the support and information provided here helpful in your concours related efforts.
To your questions in no particular order
1- The stamped numbers that match on your heads and block are most likely rebuilders markings that tie the engine to a work order. Ford engine VINs were not stamped using a gang stamp
2- Given the location of the 0A13J its likely that that is the base engines assembly date with assembler's initial.
3- Interesting and unusual IMHO that the intake, heads and block were all cast on the same day. Don't recall every seeing that happen.
4- "Matching numbers" is a very deep subject and the term can be used to describe any different things and situations. There, at the moment, no standard definition in the hobby that I'm aware of that everyone accepts and goes by.
5- Have you looked and inspected this surface of the engine block?