23 spline v 18 spline

Sorry but 1966 was the first year for slipyokes and all 440-4 and 440-6 and 426 hemi 4spd cars came with 18 spline, that's why there are so many out there. 426 wedge, 400, 383,360,340,318,273,and /6 came with 23 spline 4spds, the 66&67 273 and /6 A-body cars had the small (904) slipyoke. The only ones I am not sure of are the 1964 hemi and max wedge cars. I think they where the reason for the 18 spline to be built.