Arouse the DAMPFHAMMER!
312whp with cr 11.5 and 91oct???This is probably the article he was reading:
Building the Naturally Aspirated Honda K Engine! Part 1 by Mike Kojima The Honda K series of engines is one of our favorites and one of the top production inline…motoiq.com
312whp @ ~8000 rpm (Church's whp) on 91 octane
My vote is build it with what you've got and have fun with it. Use the manifold and forget the ITBs. If you still feel it's not enough, for the budget required to get to 300 at the wheels, build a second motor. A new block is a drop in the bucket compared to the cost of the pistons, rods, sleeves, machine work, port work, cams, valve train etc. etc.