I have been very happy with the work that David Clements has done for me. That being said there are several good smiths that can do the job for you. John or Dustin Linebaugh, Bowen, Jim Stroh of Alpha Precision all do outstanding work as well. Most of these smiths have very long waits so if you want it soon your choices will be limited but be wary of any smith that does NOT have a backlog as quality custom revover smiths are in big demand. Also expect it to be expensive as quality gunsmithing always is.
The better smiths dont turn out large numbers of conversions per year so they have to be expensive just to make a living.
Best of luck with whoever you choose.