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Good morning! I’m looking for a new set of main bearings in 0.010”. My usual go-to sources (Kanter, Merritt, Terrill, Egge) don’t have or make in that dimension. Does anyone know of a source anyplace else that might have them? Found a set on eBay a couple of months back. They were not all in like-new condition, but we’re determined to be usable. Once installed and bearing caps torqued, when engine was manually cranked, we noticed engine was harder to crank than expected. Caps were removed and bottom half of bearings were inspected. Some show “witness marks” at various locations, i.e., where they meet opposite bearing half or in other areas of the bearing surface. Don’t really want to have the crank ground again to accommodate 0.020” bearings unless absolutely necessary. Any alternate source suggestions are appreciated. Thanks!1

I don’t know if it’s possible but maybe .020 over bearings can be reworked to the size you need as they are thicker than .010 bearings.

Bearing sizes are relative to shaft size. A crankshaft that has been ground .010" is undersized, so a bearing is described as "ten under".

If the bearing is tight at the parting line, check the cap alignment, it should fit tight in the register. Are any of the caps reversed or swapped?

What is your bearing clearance, and method of measurement?

One of those things to check before the crank is cut, aka, Oops! These things take some planning.
From surface, if 20 over is available, I see that the best option => recut
0, 20, 40, 60 is kinda "std." for rework on bearings and pistons. Maybe a more numerous motor might have more repair options. I didn't like taking 40 from cylinder wall on the Cad, but that's what was available. They won't last forever, and probably won't see that much service going forward to be over concerned.
Find a better engine shop and see what they say. Maybe they can check straightness and align hone, maybe not. There are valid reasons why they went away from bigger inlines. Such a long crank may have deflection.
It is possible to add material, flame spray, etc. but not your usual machine shop task and cost. It's a commercial mostly item. Either way it's gonna come out of there again.