They need to be fitted more often than not. If it was a convertible it can be sent to Ruger. If it was built strictly as an ACP only gun, I'm not sure if the factory will fit one or not but plenty of gunsmiths will.
Do you have a pic.
I really enjoy ACP single actions. Quite practical field guns. Just as an FYI in case you did not know, 1911 mags make great "speed loaders" for single action .45 ACP revolvers.
