the 600's are the same size venturi and throttle bore size that street hemi's, early s/s wedges and IIRC the old 409's had; definitely not on the large side. keep in mind that chrysler offered a larger set of carbs for the '67 hemi's (which were identical in throttle bore and venturi size as '67 440-375hp and '64 wedge s/s and 750 edelbrock) because the original carbs really weren't big enough. add another 75 cubes and the idea of larger carbs is more enticing. don't let cfm ratings and all that muck control your choices. the 650avs2 has a little larger secondary than the 600 plus an adjustable air valve. i also like the annular booster. i've been up/down/sideways and every direction you can go with my carbs and the truth is they're close to being the way they were as they came out of the box. i've always wanted to try a pair of 750's (they don't really do 750cfm) but been too cheap to buy a new set of carbs. i do believe my engine wouldn't have any issue with 750's. as far as WOT throttle goes my carbs are very smooth. no hesitations, hiccups, bogs, nothing; just smooth power. i run a progressive linkage like the street hemi's which is good for driving but not the greatest for trying to pedal the throttle in low gear. this set-up will flat blow-off the 275-60 tires i have on the back at will in low gear from any speed. very good mid-range power; even with a 3.23 gear. i can lug the car down to 15mph in high gear and just give it some throttle and it cleanly drives away. these quads are also the cleanest burning fuel system i've had. i used to be a die hard 6pak guy but this set-up has really changed my perspective. i like 6paks for shear power in a street engine but considering a ch28 set-up is half the price with fewer headaches the choice gets simpler. i'm not a fan of big holley type 4bbls and single plane intakes for street driving. they don't necessarily make power because the single carb is so wonderful but because the intake manifold flows more air; sometimes a lot more air than a dual plane. but, large venturi and throttle bores don't always mix air and fuel good at low rpms and for what i do i don't want to give up torque below 3500rpm.
