I have exactly the same problem with my Satoh S-450. Did you buy the Woods 25mm X 18 spline yoke and did it work? I didn't want to spend $70 unless I know it works; I called all of the Woods dealers in my area and none had the yoke in stock.
/ satoh 370 & tiller, missing 18 spline yoke to run tiller. can i make/ buy one
The yoke is not a big seller so it would not make sense to stock it. I think I would check with these guys, they probably have the yoke or an adapter to 6 spline. Sheaffer's Town & Country Tractors Inc. | Dixon, IL