I am looking to try a trigger shoe on my four screw Pre k-22. It came shipped with a target hammer and target grips.What is the correct ACE number for my gun? (I heard these were made in that period). Also i have never tried one. Is there anything i should know about fit. It was my first k-22 and its mint so any chance of harming finish? I enjoy a target trigger on my 19-3. Thanks...Rich