I'll be really surprised if it gets close to 400 HP,I was cutting my teeth on hot cars and hot rodding in the early 1960s, lots of Ardun powered street rods got their clocks clean regularly by dual quad 1957 Chevy 283 motors that had been hop up a little in 1957 Chevy bodies
Those little carbs don't help either.
Do you know which block was used and how many C.I. it has now? Those blocks only had three mains caps, spin them up to far and the pin would fall out of the grenade and go BOOM
Sorry to be a party pooper.
I really hope they break or make over 350HP
Please keep all of us in the loop