Tim,
You have to know what intake manifold type to know what cfm. Example ; I run 2 - 600 cfm edelbrock carbs on a blue thunder dual plane manifold. The dual plane manifold splits the engine in half and even at wide open throttle any one cylinder will only 'see' the left half or right halves of the 2 carbs. So the dual carbs act like a 600 cfm setup instead of a 1200 cfm setup. The fuel distribution is better with 2 carbs than 1. Now if you have an open plenum dual quad manifold like a tunnel ram, you will see all 1200 cfm at once and have very poor low end driveability and mileage. You are running an 800 cfm carb on an open plane intake , each cylinder will 'see' all 800 cfm at any one time so it could be too big for your application. The intake manifold has more influence on the way power is made in the engine than the carb does so I would think about that first ,then decide what carb cfm you want to run.
Perry.
