I just got an 69 S50H with the same setup. There seems to be a directional valve if you look at the rear of the pedal assembly. There is only about 1/4" of travel on the reversing rod. I've noticed a light click when it selects between direction. I sprayed all the pivots down with Lube it All, because sometimes it was not changing directions easily, and it seems to work smoother now. If you look under the pedal, the reverse side has a small gap and the pedal rocks to that side.