Cook 5 slices of bacon in a large skillet until crisp. Remove bacon, reserving the drippings in skillet. Crumble bacon and set aside.
Saute onion in reserved drippings until tender. Add tomatoes, molasses, salt, chili powder, pepper, mustard, and crumbled bacon; cook over medium heat 35 minutes. Combine tomato mixture and beans, stirring gently.
Spoon beans into a lightly greased 13- x 9- x 2-inch baking dish; top with remaining bacon slices. Bake at 350° for 1 hour. Serve warm in baking dish.