11 C4 input shafts and forward clutch hubs changed three times. From '64-'69, a .788-inch 24/24-spline input shaft and forward clutch hub was used. In '70, Ford used a .839-inch 26/26-spline input shaft and forward clutch hub. From '71-'82, a .839-inch 26/24-spline input shaft and forward clutch hub was used. The 26/24-spline shaft is 26-spline at the torque converter and 24-spline at the forward clutch hub. The shaft on the right looks more like a C5 input shaft with a hydraulic passage for a locking torque converter. Keep this in mind when you are shopping for an input shaft. You want a C4 input shaft, not C5.