Has anybody changed this freeze plug? I cannot find it anywhere online and nobody lists a part number. Mine is a little too rusted for comfort... This is the one that fits inside of the thermostat housing cavity on the opposing head (drivers side). I measured mine right around 1.380". Any help is much appreciated!

 

Welcome to the forum

Never had to replace that one, you are correct it doesn't seem to come up as a freeze plug, core plug or expansion plug
Left and right heads are the same casting, so they just block off the thermostat opening on drivers side rear

Best bet it to pull out the old one and go to parts store to match it up
I would use a rubber expansion plug myself to replace it, more expensive(which is why automakers don't use them), but it won't rust