For marinade, whisk together bourbon, soy sauce, molasses, vinegar, and chili powder. Remove 1/4 cup for sauce. Prick both sides of steak with fork. Place in self-sealing plastic bag set in shallow dish. Pour marinade over. Seal; marinate refrigerated, 2 to 3 hours, turning occasionally.
For sauce, in saucepan combine ketchup, 1/2 cup water, 1/4 cup reserved marinade, 2 Tbsp. butter, and 1/4 tsp. pepper. Bring to boiling over medium; set aside.
Remove steaks from marinade; discard marinade. Brush meat with 1 Tbsp. cooking oil. Let stand at room temperature 30 minutes.
For charcoal grill, arrange medium-hot coals on one side of grill. Place steaks on rack directly over coals. Cover and lightly sear on both sides, 4 minutes. Move to unheated side of grill. Cover and grill 12 to 15 minutes more for medium rare (145 degrees F). Remove; let stand 5 minutes. Butter bread; place on hot grill. (For gas grill, preheat grill to medium-high. Adjust for indirect grilling. Grill as above.)
Reheat sauce. Thinly slice steak and arrange on toast; pass sauce. Serves 6 to 8.