904 Spline Count

The transmission in my car was built by Cope Racing Transmissions. Purchased/installed by previous owner.

After showing CRT pictures of the shaft (pictures from previous owner) they state it is a 24 spline shaft. Transmission is still installed in the car or I’d simply count the splines.

All the research I’ve done says 904’s had either an 18 or 27 spline shaft (non locking).

Is the 24 spline shaft from a 727? Is that a common modification?