Exactly. The cable shift units only had the throttle pressure shaft that came through the case and used the seal. The shift cable entered below and forward and used an O ring seal. As John said, in 1966 when the linkage type shifter was introduced, there were now two shafts that come through the case. The shifter shaft is larger and uses a metal backed seal that is pressed into the case while the throttle pressure shaft now comes through the center of the shifter shaft but uses the same seal that used to be in the case of the previous cable shift units.