New oil pressure switch doesn’t fit...318 LA

No way I would re-tap this...... that drops directly down into the main oil passage coming up from the filter and feeding to the passenger side oil gallery.... which feeds EVERYTHING.

Figure out what the threading is and buy an adapter. If one cannot be bought, then have one made from a bolt, drilled through with a hole for oil, and the threaded on the outside for another adapter to go to the proper NPT thread.