CARB SIZE???

[88PONY]

I was wondering what you carb people would put on my combo. I have a 306 Edelbrock performer RPM heads milled .030,1.6 rockers, Comp cams 565-575 lift with 234 int-244 exh @50 11.1-1 comp. Victor Jr. intake 15/8 long tubes/with 21/2 pro chamber and race magnums dumped. It has an ATI c-4 full manual/no brake. The converter is a 4200 8in. I also run a 4:10 rear. I ran the car before it was even tuned and it did the best of
12.401@108mph shifting at 5800rpms leaving at idle. I have a Holley 600DP 4150/with mechanical secondarys.The jetting is 66front/76rear. It seem to be fine, but above 6500 it starts to break-up a little bit. This engine was built to rev, and was estimated to have 500hp. Some people are telling me to put a 750 on some say 600 is fine some even say a 900. Come on now this is still a small motor. I think a 650-700DP would be good but maybe someone out there has a similar combo that could help. I just don't want to spend $400 on the wrong carb.
Also I do drive this car on the street occasionally
Any help would be great.

Thanks Guys/Gals