Not sure if this helps, but it may point you in the right direction.
Year Model
1962-1977 727 (Non Lock-Up) Lock-Up has hole through input shaft, 18-1/2″ extension housing.
1978-up 727 (Lock-Up or Non Lock-Up)
1962-1977 904 (Non Lock-Up) Lock-Up has hole through input shaft, 14-3/4″...