Kent,
Thanks for posting a reply to my question. But, I do not understand your comment.
Are you stating that because the sights are factory installed, the dovetail slot in not tapered nor the actual sight. I did not state, that I wanted to remove the existing sight in order to replace with a new marble sight. So, are you say just punch it out from left to right (standard approach) then taper the dovetail with file a little, then slowly work the new sight to fit the new dovetail taper.
Sorry about this, not use to working with this type issue. Even Uberti rifles have an existing taper.