If your pushing towards 900bhp its all about head gasket integrity. If they want to push Power limits this will have to be addressed. I wish them well testing this block, writeing off a few engines aint cheap .
Beefy- The EVO's can easily push past a 1000bhp with no special gasket measures because although all heads must lift their integrity is not comprimised on that more modern engine , I wish i could say whats been done to mine to try & replicate that on a YB. If they were starting with an EVO engine I think it would be a better starting point. It can never be a YB so why take a 40 year old design as a starting point.