They aren`t core holes . I checked both my shop manuals ... 60 to 64 Galaxie and 67 Fairlane in the 427 section . Back then , all 427 engines came with an
oil shield on the bottom of the intakes and one also between the heads in the valley ( valley pan ) ... and I remember that when I changed manifolds on my Galaxie last summer , there was the splash shield on the manifold and on the engine also .
Those 4 holes are for mounting the
oil splash shield on the bottom of the intake(s) . It kept the manifold a little cooler and helped the incoming mixture stay a little cooler . Make sure you use some red loctite on those screws .
Bob