Norm,
Welcome to our group.
When asking such questions, you must provide the serial (PIN) number of your TRACTOR. The 446 model was made from 1972 to 1988 and several differing exhaust systems were used. Your question is sorta like saying you own a Chevrolet and you need a muffler for it. :sidelaugh:
Once we know what you own, we can better advise you if what you are looking for is even still available. :thumbsup: