Help me identify these (3) 292 Y block holes in block

[bullrunmotor]

I'm cleaning up a known running 292 motor for a project. Putting on new gaskets-chasing out threads, painting and noticed 3 holes on the passenger side above the oil pan. the center one appears to be full of some kind of sealer. The left and right ones are clearly 3/8 course thread and just plugged up with grease/dirt. There were no bolts/plugs in them nor were they used in the prior application. Can anyone tell me what they are for and should they be closed off with perhaps an allen screw etc. ? First experience with Y Blocks. I've enclosed photos. Sorry photos won't post-will try again latter. Thanks in advance