Cook manicotti shells according to package directions. Meanwhile, in a large skillet, cook sausage and beef over medium heat until meat is no longer pink. Add garlic; cook 1 minute longer. Drain. Remove from the heat. Cool for 10 minutes.
Drain shells and rinse in cold water. Stir the mozzarella cheese, cream cheese and salt into meat mixture. Spread 2 cups spaghetti sauce in a greased 13x9-in. baking dish.
Stuff each shell with about 1/4 cup meat mixture; arrange over sauce. Pour remaining sauce over top. Sprinkle with Parmesan cheese.
Cover and bake at 350° for 40 minutes. Uncover; bake 5-10 minutes longer or until bubbly and heated through. Freeze option: Cover and freeze unbaked casserole. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake casserole as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165°.