Soak dried shrimp in warm water to cover until softened, about 20 minutes; drain. Coarsely chopped
To make meatballs, combine shrimp, pork, stock, water chestnuts, green onion, preserve vegetables, cornstarch, soy sauce, oyster sauce, and sesame oil in a large bowl; mix well. Cover and refrigerate for at least 30 minutes
Soak bean thread noodles in warm water to cover until softened, about 5 minutes; drain. Cut in half
Remove outer leaves of cabbages until their diameters are 2 1/2 to 3 inches. Trim bases to flatten. Cut top leaves off to make cases 2 1/2 to 3 inches high. Remove inner leaves to create an area for stuffing (save trimmings for another use if you want). Spoon half of meatball filling into each cabbage case. Tie kitchen twine around case to secure
Prepare a wok for steaming. Place noodles in a heatproof dish. Place mushrooms, gill sides up, on noodles. Stand stuffed cabbages on dish on steaming rack. Cover and steam until cabbage is tender and filling is barely pink, about 30 minutes. Remove twine and replace with blanched chives before serving. Garnish with bell pepper