Joel- thank you, I'll ask him again and maybe ask him to get pics. He is in the DC area so it'll be a bit before I can get to the car again. That sounds more likely for sure. I'll have him do more inspecting!
I believe the large holes are jig reference or positioning points for machining. No core plugs. I suspect the leak is at the rear core plug area. Hope it is not a crack. He most likely needs the transmission removed for proper inspection.
That was my first thought as well, I thought those were only used as reference points, but the one pic looked like a core plug so I figured I'd ask.
I assume this is a coolant plug as well, circled below? The two on either side of the cam are oil galley plugs.