Once your hole is finished, be sure to blow out the chips.
Get your Loctite or JB-Weld ready. Put the slightest dab around the edge of the plug and press it back in. It should seat up against the existing shoulder. I smeared a bit of JB-Weld at the top edge, so that it can't move, but this is probably overkill.
(If by some chance, you buggered the plug when you removed it. You can still save things. Tap the bore 5/16"-24 and make a short plug out of a cut-off section of bolt, no more than a quarter of an inch long. Cut a slot in one end for a screwdriver, and install it in the threaded section with a dab of loctite. Be sure not to make it too long, or it will interfere with the mixture passage behind it. Good to go.)
