RGB, the rail mount used on the MS rifle you are looking at will have a 70 degree rail which is the system used on the older rail mount scopes. No new scope will have that system. Most use the Zeiss rail or else Swarovski and S&B both use their own. If you want to use a new scope you will need to change the front mount and base plate as they come as a matched set, and the rear foot will need to be changed as well.
If you change the scope but don't want to change the bases you will need to buy a scope from that era that used the 70 degree rail.

Matt.