Recommend a 650 cfm or less carb with air valve secondaries. Because of the primary/secondary disparity, the Thermoquad and Quadrajet make the cut, too. This recommendation, IMHO, will preserve throttle response while allowing a bit performance to shine through. The benefit of the air valve recommendation is that the secondary does not open until the engine actually demands the extra fuel. While I can't complain about the DB4, the Performer can handle either a squarebore or spreadbore carb.
FWIW, I have a 625 cfm AFB, Performer, 302 heads, and a Summit (Crane Fireball) 6901 cam on a 318 in my Demon. Even with the 2.76:1 gear in it now, it's fairly peppy. Couldn't tell you about fuel mileage as it isn't a DD and when I do drive, it's not the right sort of situation to use for a good opinion.