I got a recommendation for this scope mount for my mosin. Heard many good things from the buyers. only down side is that you need a bend down bolt.
http://advancedrifleparts.com/
http://advancedrifleparts.com/installation.html
No drilling or tapping required. Just replaces the rear sight.
This is something similar to Jmecks scope mounts too I guess. pricing is pretty good I say