[Boog]

Henny the next time it shuts down pull over and remove the air cleaner and peer down into the carb while you work the throttle lever. See if there is fuel spraying down. Have someone try to start the engine while you remove a plug wire to check for spark to the plugs.
Many of us have been through this over the years. One of mine was a broken wire going into the distributor that occasionally lost connection. That took a while to figure out.
Be sure you have a 12v power source to the HEI distributor too.
Look at all rubber hoses on the fuel lines. Some can collapse with age.
Maybe something here will help.