Here’s a piece of useless, but interesting, information that I gained while working at the Flint V8 engine plant in Flint, Michigan starting in the 60s. In the olden days, I’m not sure when things changed, probably in the 70s or 80s, a crankshaft that was ground up to .009 undersize was OK for production. We had .009 under bearings that were used on the assembly line on a regular basis. Cranks .010 under or smaller were scrapped. This was for both mains and rod bearings, I believe.
Our boring machines for the cylinders couldn’t hold tolerance for bore size (a few thousandths over or under was common) so pistons were made in different sizes to fit the bores. These pistons were assigned a “letter” size and the bore size “letter" was stamped on the oil pan rail next to the corresponding cylinder, or rod bearing as these blocks were assembled at this point with the oil pan rail up. Those were the days when a 100,000 mile engine was a rare thing.
I’ve seen camshafts with undersize bearings spray welded (a process where molten metal was sprayed onto a red hot bearing journal) then reground and used for production.
Oversize rods (both big and small end) were copper plated and re-honed to attain proper size.