Bill, I got a chance today to check for a stamped part number on the 139 tooth ring gear I have on a flywheel. Nothing there.
Of course that might make sense as when it was produced, there was no 168 tooth ring gear or 12V starter, so no need for GM to spend the 2 cents in labor to stamp it. Up until 1955 or so you could walk into a Chevy dealer and say I want a starter ring gear and the parts guy would hand you a 139 tooth one.
