I had the exact same problem that you are describing in your first post. I followed all the tips that people have posted here and was able to get the car to run absolutely great with the exception that when I dropped it in gear the idle drop was several hundred rpm and the car was very unstable until I was rolling.

Larry Shepard came out with a new book on tuning and working on Mopar six pack motors. I got the book and it contained the best advise I have ever received. He said that for automatics you should richen the outboard carb adjusting screws almost one whole turn. I did it about a half a turn (from the 3/4 they were at) and it made a HUGE difference. I had to lean my center carb a bit, but now it idles in park or drive at about 800 rpm with very little difference between in gear or not. Still runs very well. A little rich, I need to tweak it a bit, but a very large difference. Drives great now!

Mine is a 440, stock motor and cam, Mopar dist set at 38 at full advance. Jets at 64 in the center carb