From what I hear the crankshaft manufactures are targeting low end of the spec or even slightly below to get the clearance where most performance builders what it. Most shoot for .001" for every inch of journal diameter so in our case .0028" clearance. If the journals where at nominal diameter it would probably be way to tight of a clearance.

Same for rod journals except that chevy journal sizes have a wider selection of under and oversized bearings.

AG.