GM drilled all their 235 crankshafts for a pilot bearing, but did not machine the rough hole for a pilot in the cranks they used for the Powerglide since it did not need one. (Saved a few bucks.) Therefore, they did not make a pilot bearing to retro the Powerglide crank to a manual tranny...
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.
