PCV issues?/hesitation

Followup note. I had dismissed the accelerator pump as the issue as it pumps perfectly when installed on the 440. Did you also note my comment that the idle mixture screw has no effect, even when screwed all the way in.
I considered trying to determine what the OEM carb was, but once again, if the Rochester works on the slant 6 440, why not the Dart?
There is a snake in the grass here and my instincts tell me that it's related to the PCV system, or a vacuum leak. I have closed the vacuum port to the heater controls and nothing has changed. Other than the missing hole in the manifold, the carb gaskets seem to have the right configuation for matching the carb base and maniifold.
I'm sure that one of you has an answer for me!