I'll probably use 9/16-12 Grade 8 bolts on the inner holes, and drill and tap the block for 7/16-14 Grade 8 outer bolts. Studs are OK if the block area where the threads are located is pretty beefy, but that's not the case on a stovebolt engine. It's also necessary for the cap and lower bearing shell to self-align with the crank as the bolts are torqued, since a stovebolt does not use alignment dowels or a stepped block to positively locate the cap.
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!