Dying Dart after being warmed up.

Hello awesome /6'ers!

My 71 dart is coming back from the paint/body shop on monday and can't wait to show you guys pictures! In the mean time I was hoping you could help point me in the right direction with the only mechanical problem the old girl is having right now.

First off its a bone stock 225. Right now she starts right up and idles great from sitting over night. Driving from there seems fine, idle seems ok to me and seems to accelerate as well as a 40 year old /6 should. But intermittently (I would say 75% of the time I drive it) after about 15-20 of driving she'll start to sputter out and die when left to idle. Like I'm cruising and it seems to run fine, but once I get to a stop light it dies. To start it again I have to turn the key and keep the RPM's up while in neutral. I'll take off it stays alive at cruising speeds, then dies again once the RPM's get to idle. There have been time where I had to drive it like this for 15 minutes or so to get back home and sometimes the problem seems to fix itself the it can stops dying.

My first instinct is that the symptoms must be associated with heat, but the fact that it sometimes goes away (without getting any cooler) confuses me.

Any advice on where I should start the diagnosis? Retune the carbs idle adjustors? Vacuum tests? I've only had the car for a month or so, and am still learning a lot. Any advice would be awesome gents!