I recently purchased a 1986 John Deere 650 Tractor. I'm totally in love with this little guy.
It came with a belly mower and it has mechanical front wheel drive, but the front drive shaft was missing. After an exhaustive search for the 15-spline yoke, I found a shaft for a John Deere 755. To my good fortune all I had to do was shorten it up quite a bit, and both ends fit perfectly. I found a John Deere 4-foot rotary cutter to use as well.
I'm the 4th or 5th owner, but hopefully they last. I can't wait to put it to work!!