Its either 26 or 28. Car is a 75 maverick with a c4. And how hard is it to change with the motor completely out of the car?
if the car is a 75 with the original tranny the front shaft is a 26 spline. they changed from 24 to 26 in 1970. if the engine is out the TQ just sits on the tranny input shaft. it is connected to the flexplate by 4 nuts. if the engine is out don't let the TQ just sit on the input shaft. it'll ruin the front seal which should be change out if you have everything else out of the way.
The input shaft (the one that slips in and out) is twenty-six splines. The stator support (the one that is part of the pump) is 32 splines.