318 missing and stalling once warmed up and at cruise

Check the reluctor gap in the distributor... .007" with a brass feeler gauge between the rib and the pick up....
Would this gap , if incorrect, only cause a problem once the engine is warmed up, and only whilst coasting/idling, and NOT under load?... If so, are you able to show me a pic of the actual parts you are referring to? I can check with a feeler gauge in the morning!