One other thing you might try is epoxying the scope-mount base to the action. I know more than one gunsmith who's used this trick to deal with 98 Mausers where a screw-hole can easily be buggered, or even become slightly loose, because the thin bridge wasn't originally designed for scope-mount screws. In fact, this is the way my .375 H&H Mark X Mauser's rear base is mounted, using Acra-Glas Gel. If you decide to change mounts later, it can easily be removed by heating the base.
You can also have the mounting holes converted to larger 8-40 screws, but that doesn't solve the problem of very few threads inside the hole, which often causes the problem in the first place.
The last smith to touch this rifle did just that to clean up the messes from the other smiths. It appears to be holding.
