There are several that give you info on removing the motor from the frame. I would either go to a repair shop or bookstore and look through them. Also look at some repair sites. Go to mtdproducts.com Check out the owners manuals. You will need the model and serial number to look at most manuals. E-mail me the numbers and I will see what I can find for you. cholbach@yahoo.com. You also said that you had one with a good motor and one with a good deck, why not switch out the decks? Might be easier for you.
cholbach
October 2005