Two different carbs with the same results leads me to believe the manifold with the adapter is causing your problems
Is your intake a early or late 440-2? The early ones have individual raise bumps on the intake runners for injector use, the later ones have one oval boss that sits across two intake ports down low next to the heads. I don't remember now which one has the intake port wall divider sticking out into the plenum under the carb, the other one doesn't have that
IHTHs