First off I apologize for not being able to search the forum, I suck at it.
I have a bare head from 1975 which appears to have an EGR port located at the side rear right next to #6 intake. This port is channeled to each exhaust chamber right below the exhaust valve near the stem guide. First, what is this port and second can I / should I block it? With each exhaust chamber connected to it I'm wondering the best course of action. Probably over thinking this...

Nothing special there about "1975". But the original engine that head came from had an A I R pump, for smog control.
You can block that off if it isn't needed. I have one here like that as well. One of my spares at the moment.
The head I have with that port is the same exact casting number as the one on my most recent build that doesn't have it.

Thank you very much sir. Appreciate the info