Anybody go to the trouble of tapping their freeze plugs?
Looks like 1 5/8" is common size, would then if going typical to O ring boss #24, would need a 1 7/8"-12 thread. How tough to do and worth it? Make it easy for future reverse cooling if desired seems to me.

Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.