What octane should I run

Try it and see, read plugs and go easy with the tune so sneak up on it. There's more to detonation than just octane, same guy said he'd managed 21-1 compression on pump fuel BUT this guy was in his own league.
I've definitely got a new learning curve to figure out now, since this will be my 1st tunnel ram deal ported with 2- 850s, if this was a street car I'd go all in on tuning it for pump gas and surely the plugs will tell the tale.