Suggestions on who can convert .44 mag Ruger cylinder to 44-40?

Andy Harvath
Alan Harton
Jack Huntington
Hamilton Bowen
Bobby Tyler
Isaac Gallagher
John Linebaugh
and others if it can be done using your cylinder.

emailed Bobby Tyler. He said it couldn't be done. I see a .429 pilot 44-40 reamer in my future.

You may need to start with a .41 magnum cylinder. That is why I said "if it can be done with your cylinder. Ask more than one gunsmith, if they all say it can't be done then, proceed from there.