Guess I should have read better, didn't see the 700hp goal. I agree, a 464 is happier in mid 600s. I know 2.5 chargers make more than that but they are a rare breed.
I made 820/1778 on Duramax Tuner's 4wd mustang dyno at ~52psi of boost on a Bullseye Batmo gen 2 475/87/1.00. With a retune from someone else (at the same fuel quantity) it picked up 15-20psi of boost (went to 71psi before the charger popped) and was noticeably quicker, how much I will never know.