‘71 Dart with 340 motor stalling problem

Have you checked to see if you have fuel in float bowls when this occurs? What does your fuel system consist of? Have you loosened fuel cap when this occurs? Could be wrong fuel cap or a vent system plugged. If it does stall and you loosen cap and hear it pulling in air that could point to vent system. If you have factory exhaust manifolds do you still have the butterfly installed on passenger side. Maybe it’s stuck partially of fully closed. Does it have a choke and is it operating correctly. Just some things I’d check personally.