don't know where you are located. i have had good luck finding engine parts for my cockshutt 80 through Continental Engines in Edmonton AB.
James is the man to talk to. They still have some of the books on these old engies and access to people to get the parts. They can be reached at (780)426-3890 or by fax at (780)462-5899. Maybe the dealer for Continental engines in your area has contacts that can find the parts for you.Hope it is some kind of help.