Carb cfm with ported heads?

Ok so your not exactly in race trim but this was from 1986>
340 Cuda, stock heads, solid ft cam, race intake/hdrs, 4200 verter, 4.30's, 10x28's, ran 12.4 with an 850DP, all the guys kept going on at me about my carb being too big including a racer with a 3500cc Cortina, so puts my old 750DP back on and gave it a tune, result 12.6's, told that guy with the buick 215ci/rover V8 engine to try my 850 over his 600 holley and he went 2/10ths quicker, he couldn't believe it............nuff said, all these calculators for what an engine needs are a waste of time, its down to bore size/stroke/head design etc, a stock 340 motor came with an 800cfm factory carb..............go for it with a 950.