I will post a picture of the headers on those heads when I go back to NC. Perhaps the Eddy heads your brother had were indeed the ones with straight plus vs angled. My understanding is the closed chambered Eddy heads all have the angled plugs and this is what causes the problem with the plug clearance. I tried everything and every plug I could find. Would not take even a "Shorty" plug.
1968 - 383 Roadrunner 4 speed street car, Dad bought new 1970 - 440 Roadrunner drag footbrake car 6.99 1/8th 2016 - Hemi RAM 1500 - Hauls all the toys North Georgia / Central NC