I always ran Holley's and some Carters for basically stock engines, but I got a pair of Demon 750 double pumpers on the fish and I think it was the best money I spent.
All 3 carbs have their good points and bad.
Carter/Edelbrocks are good carbs for stock and mild street engines, but a little more difficult to tune.
Holley's have great performance and are easy to tune but are notorious for leaking, especially around the throttle shafts.
Demon seams to have as good of performance if not better than Holley, and they don't seam to have the leak issues, "so far" I've only been running mine for about 8 months, but they would have been leaking by now if they were Holley's. I can't say how easy they are to tune since I haven't had to touch mine except the idle and mix screws.
Unless you have a pretty hot 318, I wouldn't run anything bigger than a 600 that's plenty of CFM for a 318