You need a cylinder assy and a hand. Then you need to fit the ratchets, all ten of them. It's $200ish if you have S&W do it and you have the 6 shot cyl assy to sell.
Another member posted a few months ago that he had it done by S&W.
AS I recall he said it did cost about $200.
Doesnt sound cost effective unless its broke and S&W would warranty it.