Vapour Lock Issue

Also keep in mind that heat (even though not excessive) can cause electrical issues that can produce popping and sputtering.
Verifying a spark when this stalling and no start condition exists might be a good clue.

Heck I have even seen the connector for the distributor cause stalling and not starting until the actual connector cooled down from normal engine temps.
Just crimping the connector a little fixed the two I saw do this.