Welcome to the Forum!
While I can't recall anyone who has removed a MKIII bbl,, I'd think the thread pitch would be the same. At Ruger,, they usually follow the "If it ain't broke don't fix it," attitude. The threading has worked for 60 years,, no need to change now.
However,, I'd check with a company like Volquartsen or Pac-Lite to see. They do conversions all the time and they'd know for sure.