I used to sell a drill/tap/threading kit to make a 7/16-20 bolt go into a stovebolt crankshaft, the same as the one used on later model small block V8's. There was no bolt at all on any stovebolt sixes from the factory. They were all press fit only on the balancers. The center bolt and heavy flat washer for a SBC is usually available at a local parts store's "help" section, and those are 7/16-20.
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!