Hi Karl:
I have a John Deere 317 with 318 power Steering.
They have two 3 Point Tillers to connect to the Cat 0 3 Point hitch on the 300 series.
One is hydraulic driven from a set of rear ports on the 318 if you have them.
the other is pulley driven from the rear shaft coming out of the transmission.
The last Time I checked the shaft extention parts were available from John Deere but were quite expensive. They include a Universal Joint (similar to those used on the steering column of old cars) an extention shaft, Bearing and plate that supports the rear bearing and a double pulley. It also relocates the transmission fan.
Detailed information on the John Deere 318 can be found on a web site
Weekend Freedom Machines
with pictures. All of the tillers require the 3 point Cat 0 hitch for mounting to the best of my knowledge.