There are 3 main styles of input shaft.
- Early shaft has 19 splines. 1962 - 1966
- Later NON lockup shaft has 24 splines. 1967 to date.
- Later LOCKUP shaft has 23 splines and a turned spigot on the end. 1978 0n. It also has a fluid passage down the middle.
From 1967 some HD high horse power applications had a factory HD input shaft. It can be identified by a radial groove in the splines