He did state that the crank was undamaged and the rod broke 1" from the crank rod journal. That would rule out spun bearing.
Stock rod would be the culprit imo....
I would reassemble with quality rods and at least ARP2000 bolts! Those bolts are good to 750hp or the L19 which are good for over 1000hp... Make sure the crank is a forged piece too! BALANCE everything and use a good dampner.