Anything close to .003" will start to knock. Since you've got the pan off already, it's good insurance to install a new set of rod bearings. Polish the crank journals with fine-grit emery cloth using a shoeshine motion, clean it up thoroughly with spray solvent like brake or carb cleaner, and plastigauge the new bearings as you install them. A set of rod bearings the correct size is cheap insurance, compared to ruining a crankshaft or putting a hole through the side of the block.

I'm sure you know the old saying about "assume"- - - - - -check it and be sure! Why cut corners now when you've already done the grunt work of taking everything apart?
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!