Buy or borrow a micrometer and measure them yourself before you do anything else. That's step one. If you want to have a set of mounts made of any description you can imagine, Steve at clawmounts.com can do any type of custom scope mount machining. He can make traditional clawmounts, or a custom mount of your, or his design. And as others have said, you can also possibly get machining done on standard Ruger rings but if you remove too much metal, the caliber of your rifle and recoil might come into play if you're shooting a heavy magnum.
