My own experience would suggest you'll be leaving a LOT on the table with a 750. My 451 has an 830DP on it and it runs pretty good on the street, but I suspect it could be making more power up top at WOT with a bigger carb. OP is running 4.56's and an M1, both of which want RPM's. I would be thinking 850 minimum, larger (4150 -1000) would likely make more power and be my choice, especially for a car that is used almost solely at the track as the OP describes.