906 or 915 ?

450 HP is easy, build a quench motor. Runs on pump premium. My build: 915 heads mild port & polish flowing 270cfm, SRP pistons, total quench .040. Mopar .528-284 mechanical cam. 522HP with headers. Im guessing about 485 the way it sits.

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Is 270 cfm out of a 915 head really considered mild? I was under the impression that it takes quite a bit to flow that much.