Place steak in a shallow dish or large zip-top freezer bag.
Pour molasses mixture over steak, reserving ¼ cup for basting.
Cover or seal, and chill 2 hours, turning occasionally.
Remove meat from marinade, discarding marinade.
Sprinkle evenly with salt.
Grill, covered with grill lid, over medium-high heat (350° to 400°) 6 minutes on each side or to desired degree of doneness, brushing often with reserved marinade.
Cut steak diagonally across the grain into very thin strips.
Serve steak in tortillas with lettuce, tomato, Cheddar cheese, and sour cream.
