71 valiant engine build, which carb to use

I do like the looks of those demon carbs, I know they perform well. I really like the idea of dropping the 800 cfm edelbrock on there and not looking back, especially when it is a new in the box and on the shelf part. Just wanted to be sure it's not going to overfuel it or starve it with the 600 cfm.
I have 1200 cfm's on my 318.... (a pair of 600's), and it's nowhere near the motor you are working on....