Hi number RIA 1903 help needed

Recently purchased a very nice condition hi # RIA O3. It has had a Lyman #48 receiver sight installed. My question is this, the rear sight has been removed and the tabs ground off rear sight mount. Can this mount be removed and anO3A3 top hand guard be installed which extends all the way to receiver.

You are going into a can of worms. It certainly can be done, but what will you have when done? Could you post a photo or two? It may well be OK as is, but you make the final decision.