Oh Boy. Dont get all ya knickers in a knot.
Ive used both 600 and 750 vac square bore Holleys on my Mopars. They work ok, but Holleys do have a tendancy to "suck the Joose", leak fuel, and get vapour lock.
Ive also used a beat up 383 AVS, and those things work like a charm, just like the are suppose to be there.
But my Favorite carb is the big Ol Scary, Spaceage carb ...the Carter Thermoquad.!!
What a great design with fantastic drivability, brilliant throttle response, excellent fuel useage, never heat soaks or leaks fuel. With the added bonus of that Huge intake noise when the 2 1/4" secondarys open up...If ya dont know what I mean, watch "Blues Brothers" again, and listen to the intake raw of the '74 440 with a thermy.
The TQ can be fiddly, but once its sorted is way ahead of the mainstream Holleys, and on Par with annular race 850s/ Demons etc.
Admittedly, they are all second hand now, but most parts are still available, and make a real headf#$@ statement to everyone, when you open the hood.
Only Problem is they are a Spreadbore carb, so you need an adaptor, or the correct manifold pattern.
I love them and am building a big primary one (440 TQ) for my stroked 340
,( 360), to put in my 69 Dart again, Should run high 11s with a .508" 3500 stall, 4.1s....High 10s with some sniff.