65 Barracuda daily driver

You might want to run an additional ground wire from battery negative to the alternator case, and from battery negative to the voltage regulator housing. It's sure sounding like a ground issue to me.
Just went on a test drive and the car stalled again after driving on the freeway. I was so confident that I had figured it out... I noticed the ECU screws don't grip very well - that might be very likely culprit and I will get the next size self-tapping screws. I just cleaned the connection from the battery to the engine block. I will replace the ground strap from the engine block to the fire wall and clean up the bolt and run ground wires to alt and voltage regulator. This is driving me crazy. I still don't understand why it would start when cold, but not when hot. I think I remember that electricity flows better the cooler the temperature - could that be it?