We ran a Carter 400 CFM AFB on a Ffoorrdd 300 CID with standard transmission for many years and several hundred thousand miles. Worked well. I wouldn't like to use a larger one on a street engine though.

If we were going to do it again, would use a spread-bore (Rochester Q-Jet or Carter TQ) because of the small primary side.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop