Can you tell if a block has 1 or 2 piece rear seal without opening it up???

[Grit dog]

I believe I just learned (buddy assembling up a 400sb he just had built) that the thick front main gasket is only ‘77? and older engines.
If that helps.

 

[bucket]

I believe I just learned (buddy assembling up a 400sb he just had built) that the thick front main gasket is only ‘77? and older engines.
If that helps.

I thought it was '74 and older.