In 2001 when Tapco went from Gen I to Gen II AR15 riser mounts, I called them up and negotiated a quantity price on Gen I for $9 each.
I knew Gen I were just a big block of anodized Aluminium in the shape of a Weaver rail on top, and I could mill into shapes on the bottom, like for Mosin Nagants.
With the Ruger #1, I had kind of a hard time getting the Ruger Rib off. The screws are in tight. Very well made. It is like a short shoulder bolt.
I knew I only had to mate accurately around near the screw holes, and clearance every where else. Then put epoxy between the mount and receiver.
Since then I have noticed that the very cheap ATI scope mount for Mosin Nagants has contact ribs that act like V block force multipliers.
Who would have expected great design, quality, and usefulness from ATI?
So if I make another Ruger #1 scope mount, I would go for those out rigger contact points.