Make sure your timing is correct before you tune your carb. I think you need to go back and take a look at that reman distributor. It's possible the mechanical advance is kicking in at the ragged edge of where you're tying to set your idle (ie: the springs are too weak).
Here's an excerpt from page 4 of document titled, "Timing is everything":
By having the advance kicking-in at or below idle, the engine idle speed will tend to hunt or hang up to a higher speed as the timing kicks up and down. With an automatic, this problem is even worse, with idle speed and smoothness artificially boosted by the centrifugal advance. Toss it in gear and the normal pull-down of RPM also will take down the advance, retarding the timing and pulling the rug out from under the engine. All of these erratic idle woes are the reason to provide a buffer of a couple hundred RPM from idle speed for the centrifugal advance curve kick-in.
Here's a link to the entire document. Worth reading.
http://www.jefframin.org/library/distributorRecurving.doc
