Heat oven to 350 degrees F. Spoon 2 tablespoons of the Alfredo sauce into an 8"X11" glass baking dish and spread evenly on bottom. Set aside.
In a large bowl, combine the shrimp, crabmeat, egg, bacon, red bell pepper, green onion, cream cheese, mozzarella, all but 2 tablespoons of the grated Parmesan and 1 tablespoon Alfredo sauce. Mix well with hands.
Carefully stuff each shell with about 2-3 tablespoons crab mixture, mounding slightly and packing into pasta shell. Place each in prepared baking dish.
Spoon remaining Alfredo sauce evenly over stuffed shells.
In a small bowl, combine the breadcrumbs, butter and remaining Parmesan. Mix well. Sprinkle evenly over stuffed shells.
Place in oven and bake for 30-35 minutes or until hot and bubbly and breadcrumbs are golden brown.