As a career machinist for 27 years, I question whether this would be the best practice. Raw cast bores in the crank prior to being machined, as you said are .030” too small, out of round and not concentric with the rest of the machined crank. Some may be closer than others, but some bores could be offset at the limits of what it would take to clean up the bore to fit a standard bushing. If it was offset .010” it would also move the input shaft of the tranny placing undue pressure on the bearing every time you pressed the clutch it. Not something I would want to take a chance with.
You may have gotten lucky to have gotten one that did work, but I have my doubts if others would be so lucky.
A dial test indicator would easily confirm concentricity and out of round before installing a bushing and if it's .030" undersize it was probably rough bored so I think we're jumping to conclusions here.
