One of these days I'm going to get an original scope and mount for mine but it's one of those things I don't want to buy without being able to see one up close and personal first. I have a K-VAR and McCann aftermarket mounts, both are very well made, solid and work just fine. The K-VAR is a quick detach throw lever design similar to the original and the McCann is secured by two 1/4-20 cup point set screws. The McCann is about 1/4'' taller than the K-VAR, which is about as low as one can get and still clear the rear sight aperture housing when sliding it on the dovetail.
I got my 49/56 8 or 9 years ago at a gun show. It was still sealed in the shipping box and the guy I bought it from was selling it because ammo was difficult to find and he also had one of the .308 conversions. I took it to be new unissued but it may be a rebuild I'm not sure. 4-75 is stamped on top of the bolt carrier and is the only date I see. Never had it apart, haven't had a reason to so far.