I get what you’re saying but from a practicality standpoint, the stated goal of 700 hp has to be easier and cheaper to accomplish with a 500” + BB. I get the OP has the good SB stuff already and changing to a BB is a PITA but that said, (IMO) the goal will be harder to reach and will be harder on parts staying with the SB. A 512” with decent heads and 2 1/4” headers you’ll be well over 700hp.