too many to list here, but the major changes were from 77 to 78 model was a new grain bin with floating bin auger. There was a major change to a full range VS cyl drive in M2sn 19901 and l2 17501 and up - no more pulley changes to change cyl speed, and the long shoe sn 19501 on the l2 and 21901 on the M2. Walkers remained the same. BTW the walkers in the M2 are wider than the l2