The Stovebolt Site Forums The Shop Area Engine Shop Spark Plugs for 41 Chevy 1.5ton with 216?

My dad has what I'm pretty sure is a 41 Chevy 1.5 ton that was "converted" to a tractor back in the 70's. He's running AC M8 plugs, but they are getting a bit long in the tooth. Are there any more easily obtainable replacements?

I'm pretty sure these would be 10mm. Correct?

Thanks