TH, Alpha Precision, and Bowen do these conversions on S&W L frames and Ruger GP-100s. Clements did mine,but no longer works on L frames. K frames would require a 5 shot cylinder, I think. Mine cost approximately $400.00. Jim Stroh at alpha Precision has a web site and a message board for Questions.
Google Alpha Precision or Bowen Classic Arms.
Thanks for posting those pictures for me.