my Low dollar 318 hop-up project

Hmm nice! That reminds me of how I used to true up an aluminum head for a small engine. I would take a nice piece of flat plate window glass and lay it on my shop table.tape a peice of 320 grit down,and rub the head in a circular motion .Im thinking this would work for a phenolic body also. Those well plugs on the other hand ,if leaking ...well those are a bit of a problem to remove without destroying.

Yes sir. You're on to something there! I'm not familiar with the well plugs but if they are anything like the leaky metering well plugs in the Quadrajet's, a little 2 part epoxy takes care of the problem.