NoMercy got it right. You will have to ship the revolver to Ruger to have the 22lr cylinder made for your frame - that is if your revolver was made to be a convertible. Give Ruger a call and have your serial number handy. If you have the model number that would also help.

As for the grips question: I have Altamont grips on my Ruger 22MkIII "Hunter." I love the grips and would recommend Altamont.