Pick the beans over and rinse. Put in a bowl or medium saucepan and cover with 4 cups of water. Cover and let stand overnight.
Bring the beans to a simmer and simmer for 2 minutes.
Heat oven to 325°.
Using a colander, drain liquids into a bowl. Set beans aside.
Add the brown sugar, molasses, mustard, pepper, and salt to the liquids.
In a 2-quart covered casserole, layer the beans with the onions, diced bacon, and salt pork.
Cover tightly and bake for 3 hours, or until beans are tender, stirring occasionally. Uncover and bake for about 15 to 20 minutes longer, to thicken liquids.
Calories per serving: 438