Weeping Freeze Plug - Size

What size are the freeze plugs on the block sides of a 71 225 v6? I plan to become a contortionist and want to have everything on hand to r&r.
Now that I have the Jeep running well I found a weeping spot that will soon rust through. I'm experiencing mixed blessings with getting this back on the road after a 20 year hibernation. Being well versed in resurrection of sleeping vehicles I realize it's another project for another day.

 

Thank you! I had perused their site and think it's 1 1/2", had hoped someone familiar could verify.
Fwiw, as I wind my way through getting the heep roadworthy I've re-affirmed my dislike of any cooling system cleaners.
This has the classic Prestone "T" installed by the heater box. It also has receipts evidencing replaced heater core, radiator core, water pump and thermostat and housing.
idk if there is an overheating issue yet... engine was not in tune, since tuned and carb rebuilt classic lack of po attention and chasing symptoms rather than cause.
I'll get it squared away in the next few, several, or many days.