We used to have a guy that new MF tractors up and down and inside and out but he's been sick for awhile and doesn't post much anymore. Search the name farmwithjunk on here and read some of his posts. I know he had talked about those tractors several times. Might find what you're wanting to know.
Go to tractordata.com and research it....simply, the TO35 came first, then the MF35, then the 135...engines and trans were/could be different for each...BobG in VA