Yes, your gun will have a well in the topstrap to allow mounting of the stadard FA iron sight or any of the common scope bases (Lovell, T'SOB. Leupold , Weigand, etc.) which will have shoulders that sit down into that well. The alumunum sight bases you describe have been used to hold rear sights by Bo-Mar, Iron sight Gun Works, MIllett and Ruger. What you're describing sounds a lot like a Ruger rear sight which was used on the very early Field Grades. In any event, and whatever rear sight you have, it is very easy to remove the aluminum sight base and sight- just start unscrewing!