Ok sometimes i'm the fool for sure so ya not alone. But i've gotta ask, how does a plug have an airleak?. In saying that, i did have one [still have] that the inside escaped [however they're made] & the porcelain moves up & down about 5mm or more. [anyone ever seen that--think it's a longreach champion--must find it & get pics]

The air leak was at the plug washer.  There was no mechanical issue with the plug, just air leaking past the crushed out washer and down the threads.  There's a clear sign of leakage on the metal part of the plug where I believe some of the combustion gas was blowing by.

The only other adjustment I made besides a newly installed plug was increased the oil pump cable adjustment a bit more to remove any slack from the cable at the idle (loosest) position.  This puts the pump setting beyond what is spec'd, meaning that when the mark on the slide is in its set position at the top of the carb bore, the pulley is rotated beyond the mark. 

I am going to reset the oil pump to its proper spec today and re-test.  If it still runs well, there really is no other factor I changed other than putting in a fresh plug and getting a good crush-washer seal.

Thanks for the update & hope it goes well.

Well.. 25 miles with no issues today. I just put another piston and ring set in it. Hopefully the seizure issues are behind me. This was a rescue anyway.. not a looker, but kept it out of the scrap heap.