Personally, I always had better luck/performance using smaller carbs.500 CFM or so. When I used 600's Holley's & 625 Carters AFB & AVS's I never got a crisp throttle response as I did when using smaller carbs, but I also did not spend a lot of time trying to tune them perfect. This might a great choice for you. A 390 cfm HP series double-pumper (#80157 might be just the ticket? But,, to me , might be too small, I rather see a 500CFM DP Holley.
My engines were never over 254 CI either, so take that into consideration.
The best all around 4bbl carb I ever used was a 500 CFM Carter AFB. I never had a bigger engine than 254 C.I. I am going to fuel injection, now.
My favorite ever of all time Carbs are a set of 3 side draft DCOE Webers. Probably closet thing to F.I.
