Start a barbecue cooker, allowing it to reach a temperature of 250 F, or preheat the oven to 350°F.
In a large skillet, cook the sausage and the onion over medium-high heat for 5 to 6 minutes until the sausage is browned and the onion is softened.
Add the pork and cook for 2 to 3 minutes longer until the meat is just heated through.
In a large bowl, combine the pork and beans, sauce, molasses, seasoning mix, and liquid smoke, if using.
Stir well and transfer to a deep casserole.
The casserole should be large enough to hold the mixture so that it is no deeper than 4 inches and no shallower than 2 inches.
Add the sausage-pork mixture and stir well.
Cook the beans in the cooker, uncovered, for 3 1/2 hours, or in the oven, covered, for 2 1/2 hours until hot and bubbling and the flavors are well blended.