Ted, would that be the same size as the plugs you commonly see on the SBC valve covers? https://www.summitracing.com/parts/...ugsVX-z9S6IwM9rPRkTDabxZkJokWJ6oxqaceqluPkCWw
I put it along side the pcv grommet for size comparison. I ordered one of the ebay ones will see if it's right. Thanks