This modification requires some gunsmithing but in MY opinion was well worth the cost and trouble.

I had my local gunsmith buddy machine off the raised imitation grip panels that are intregal with the Ruger MKIII 22/45 Grip Frame. He then drilled two holes on each side of the grip frame and installed 1911 Grip Screw Bushings in my frame (he threaded them in and coated the threads with JB Weld so they are permanent). Then it was a simple matter of attaching any 1911 Grip Panels to my MKIII 22/45.
I used the Hogue Rubber Finger Groove 1911 Grips on mine as I preferred the feel of them. However I know guys that have use Pachmayr 1911 Grips on their MKIII 22/45's and yet others that have opted for Custom Wood 1911 Grip Panels for their MKIII 22/45's.
Had I had the tools necessary to do this myself I am quite sure I could have done it. The hardest part is maching off the raised portion of the Ruger Grip Frame to get it flat & flush.
I think this was a very worthwhile conversion and totally changed the way the Ruger MKIII 22/45 fits in my hands. My nephew handled my Ruger and promptly had his done also the same as mine.
Larry