68 GTS won't stay running

Hi guys. I'm new here and in desperate need of help with my dart GTS. It has a 340, 727, 8 3/4 with 3.55. It was a fantastic running car but now for some reason it won't stay running especially after it has warmed up. I am at a total loss. I put a new battery, voltage regulator, coil, spark plugs, wires, carburetor, ballast resistor, and no change. Same thing happens. Starts fine, runs until sufficiently warm and cuts out, then will not restart with vapor lock or flooding symptoms. Will only restart after sitting for some time. Car has electronic ignition and was converted by the previous owner. Have had no issues for the last ten years. Never did anything but oil changes. I do not know what to look at next. It has to be something simple. It will even cut off as I am giving it gas (hold gas to raise rpm at a steady high pace and still cuts out). Any help is greatly appreciated. Thank you.