Shuts off when hot?

When it fails to start, remove a plug lead & lay the lead on the valve cover, screwdriver inside; create a 3/16" to 1/4" air gap. Crank & watch for white/blue spark. No spark: obvious; yellow spark = weak spark.
Bingo. If I had to guess, it loses spark. May not even be "heat" related, but masking itself as so. I chased an ignition gremlin from engine to engine once from a bad distributor pickup. I have never messed with points, but I still lean on the distributor losing spark on This one.