Adjust oven rack to lower-middle position; preheat oven to 300 degrees F.
Add salt pork and bacon to a large Dutch oven (at least 7 quarts); cook over medium heat, stirring occasionally, until lightly browned and most fat is rendered, about 7 minutes. Add onion and continue to cook, stirring occasionally, until onion is softened, about 8 minutes.
Add ½ cup molasses, brown sugar, mustard, beans, 1¼ teaspoons salt, and 9 cups water; increase heat to medium-high and bring to boil. Cover pot and set in oven. Bake until beans are tender, about 4 hours, stirring once after 2 hours.
Remove lid and continue to bake until liquid has thickened to syrupy consistency, 1 to 1½ hours longer. Remove beans from oven; stir in remaining tablespoon of molasses, vinegar, and additional salt and pepper to taste. Serve. (You can make the beans ahead of time, letting them cool to room temperature, and then storing in an airtight container in the refrigerator for up to 4 days.)
Notes
Nutritional values are based on one servingSlow Cooker Directions:
Prepare your slow cooker: Line your slow cooker with a crockpot liner (it makes clean up a breeze).
Cook pork and bacon: Add salt pork and bacon to a large Dutch oven (at least 7 quarts). Cook over medium heat, stirring occasionally until lightly browned and most fat is rendered about 7 minutes.
Add onion and continue to cook, stirring occasionally, until onion softens about 8 minutes.
Transfer to crockpot: Transfer the salt pork, bacon, and onion to the crockpot.
Stir in sweeteners, water, and beans: Add 1/2 cup molasses, brown sugar, mustard, beans, salt, and water to the crockpot.
Cook on low for 6 to 8 hours.
Add remaining ingredients: After cooking, stir in the remaining tablespoon of molasses, vinegar, and additional salt and pepper to taste. Serve.