First, I would examine the bases very, very carefully. Not unusual for a 'smith to "fit" the base with a bit of material removal. Now you put them on another gun and you "buy trouble" from the problem of the first gun.
#2). You can buy "shim stock" at most larger hardware stores, supply houses, etc. (Or salvage an old "feeler guage.") Put a piece under one side of the base and tighten it down. At worst, you might have to come up with some longer screws too. Same sources. Brownells has it, but you shouldn't have to go that far. Or cut pieces from an old beer can. Aluminum. Steel attracts rust. (Go ahead, get a new one and empty it for the project...) From there it is "trial and error" unless you own some mighty expensive measuring equipment. (Old buddy, retired gunsmith, had a Sweeney bore sighter with an X to look at. Sights on X, bullet hits there too. Amazing...) Sako had their own system and I wondered if they didn't "change" things now and then to get people to use their bases? luck.
