It's one of the first things that you see from anyone documenting a magnum swap. You also have a pad on the block to grind down so as not to interfere with a header tube as well as the driver side motor mount ear needing a spacer.
Yeah i have not touched an actual oem, iron headed, efi magnum. Have Just used the blocks for typical mopar smallblock builds. Basically ends up being an LA for all intensive purposes.