Just last weekend I went to my buddies house and his dad was changing head gaskets on a 390FE. He's an older fellow so i offered to put the heads on for him. He already had the gasket on the passenger side so i plopped the head on. I wipped off the block on the drivers side and when i put the gasket down i paused
...There were two passenger side gaskets! He had an easy fix, flipped it upside down and backwards which it was then actually right side up and forwards (Despite what the gasket had written on it!).
On your SBC, b/c they are so symetrical you won't have that problem, and yes, on many (if not all) of the graphite gaskets you will have passages covered. This is only a concern on the 400 blocks.