I was in a hurry and accidentally ended up with four REM40E spark plugs when I needed RHM40Es.
These have the 5/8th top threaded barrel for the lead B nut. My leads are all 7/8th inch.
SO.... my screw up can be someone else's boon if they want them. $60 plus mailing for all four. They were threaded in and then back out with a light coat of Nikal ( that is how the company spells it) anti-seize on the threads.