The shims were a production gimmick to correct for less-than-properly machined bearing bores or slightly off-sized crankshaft journals.
Definitely - use an expert to adjust it on the line rather than re-machine the parts, but of course the result is an oval bearing bore.
Curiously enough, making the bearing's major axis in the opposite horizontal plane before honing to size with a shim is a useful speed mod for very high RPM.
There is evidence suggesting that the connecting rod’s big end bore (which determines the shape and final size of the bearing shell) is not round at high speed & load, but oval, and stretched vertically by perhaps .001”. Bill Jenkins, one of the most successful Chevrolet V8 tuners of all time, used this information to his advantage when he prepared steel connecting rods for racing. He inserted .002” shims at the “parting line” between the connecting rod body and cap before re-attaching them for resizing. The bore ID was then honed .002” oversize. When the shims are removed the final bore size is nominal in the vertical axis, but .002” wider at the parting line, and will “pull” into the correct shape at high speed.
