the Dart stalled a few times while in gear at idle

A couple of thoughts.
When it dies, does it pop, sputter or hesitate at all when it starts back up again?
Did you check and set the reluctor/pickup gap in that distributor when you put it in.

Also closely check all your connectors for your HEI module.
Depending on your timing it may very well be the idle is too low.
When it dies, it just dies. No sputter or backfiring. When I turn the key it fires right back up, no excessive cranking or sputtering or flooding smell. It's essentially a clean stall and clean restart. Just as if I turned off the key intentionally and turned it back on intentionally.

I checked the gap in the distributor when I got it from you and it was fine. I will re-check it later today. I checked the connections at the HEI module and everything was secure. Also the timing is at 12-14 degrees advanced at idle last I checked.

Before I drive it I will take out the idle screws and squirt some carb cleaner down them. I'll also bump up the idle a little.