I've got a 6-pack setup from ProMax on my 440, with the tunable outboard carbs. Came pre-assembled & flow tested, I really didn't have to do much other than set the idle & mixture screws. It's been on there only about 2 years now. Car runs like an animal, but I think I could get even more out of it by further tuning the outboards.
This is my first 6-pack equipped big block & I've been happy with it.