Case 1: You lose a hero and through the 'Heroes Replenish' Scenario Special Rule (SSR) you get a new hero. As I understand it you may roll for a random location and take your free card using the 'Hero Starting Cards' SSR OR you may start at the truck and take a bonus card granted by the standard rules plus the extra card granted by SSR. Is this correct?
Case 2: You find a hero at number counter. This new hero starts only with the extra card granted by SSR. Is this correct?
That's not correct - 'Hero Starting Cards' says that that they get cards "in addition to any hero cards that they would normally start with," and under the NEW HERO FOUND Exploration Marker it says: This Fifth Hero DOES come into play with a bonus Free Hero Card.
If you get a new Fifth Hero from an exploration marker, AND you are using the Hero Starting Cards rule, you would get TWO starting cards for this particular hero.