Super Six install on 1974 Dart

Should have bought 2 plugs. The other one would be for the EGR port under 1 of the carb barrel holes. Mine were caked with carbon but I was able to chase the threads with a pipe tap. Only difference is that I used plenty of red loctite on that one. Not pipe dope.
Never know with the one that you are showing, might be some reason later that you might want a vacuum nipple in there, (add on cruise control maybe?) With the pipe dope you should be able to get it out if the need arises.
For my application I hope it never does