I would tap and plug them... they should work nicely with your carbs

Jbell, I appreciate the encouragement. I will get them tapped and plugged.

Once again, Pelican to the rescue. I can't imagine how I would have figured this out without everyone's help. Thank you.
John

There are many ways to plug these holes. I ended up with an engine with early MFI heads. The injector holes had been tapped, and allen bolts screwed in. Problem was that the bolt heads stuck up a bit too far for the PMO manifolds I purchased. Some quick work with a die grinder solved that.

But were I to use heads which needed a plug again, I'd try to use allen head set screws to get them out of the way. Or perhaps see if 1/8" aluminum or brass NPT plugs would work. Or find a lower profile bolt. Anything to keep all of the plug below the plane of the intake gasket.