The repro mounts will need fitting to the individual gun, just as the originals did. This is why they were serial numbered. The mounts will work fine once they've been opened up inside the dovetail a little. I took mine (from SARCO, 359 marked) to a really good local gunsmith who did this work. Now it slides right on, doesn't wiggle when tightened, and maintains zero when R&Red. Metal should be removed from the mount only, never the gun's rail.
Remember, lever tension is adjustable. Once you have the mount installed and tightened up, you can remove the spring circlip, wiggle off the lever, and then replace it in a slightly different position, tapping it back down on the tightening shaft splines. If you are not going to use your mount on a different gun, you might even consider epoxying the lever in position. I like steel colored "JB Weld". Now the lever isn't going anywhere, and when the lever is touching the mount, tightening tension is perfect.