help me choose a carb

I too am installing a 340 in my 69 Dart(with luck within a month) with almost the same specs as your 340(I added a roller rocker assembly).
I am going with Edelbrocks Performer RPM 800cfm(modern version of the AVS) part number 1412. According to the build up I followed it is supposed to gain 35hp(dyno confirmed) over the stock 600cfm AVS.