I’m guessing this is easily answered...

[djcdmv]

Not exactly a rebuild question, but this section probably has the most knowledge of what I’m looking at...

So I was having difficulty getting a wire hooked up to the spark plug so I took a picture in order to help me “aim”.

What are the other threaded holes for?

[Peter M]

Dave,
They're not threaded holes, just holes through the cooling fins that give that appearance, to access the head studs. Those black things with the internal hex are the nuts that hold the heads to these studs.

[djcdmv]

Thank you, kind sir. Mystery solved.