Pierce sweet potatoes with a fork. Bake at 400° for 55-65 minutes or until tender. Cool slightly. Remove pulp from potatoes, keeping the skins intact. In a bowl, combine the pulp with pineapple, orange juice, butter and salt. Refill potato shells and place in a greased 13-in. x 9-in. baking dish. Bake at 400° for 20 minutes or until heated through.