Try asking the guys at Sallee Chevrolet:
www.sallee-chevrolet.com. They do alot of work with the new crate motors and might know the answer.
BTW--great idea using a new crate BB in a 'nostalgia' application. Muscle Car Review did a story on this very subject a few years ago (before their demise) where they told how to dress-up a 454 HO as a L78. Unfortunately, I can't find any of my MCRs from that period... Good luck and tell us what you find out.