I was wondering if there is a backlash or clearance measurement for the splines on the converter to to stator shaft. I don’t really feel any ridge on the stator splines. Here are some pics

I don't know if there is a backlash or wear limit spec. I had similar spline wear but I just replaced the bushings in the existing shaft. Because I was rebuilding due to burnt 3-4 clutches, my thinking was ensure the input shaft runs true with the stator shaft minimizing the chance of leakage at the input shaft sealing rings.

I wouldn’t mind replacing the stator shaft but I hear it’s a pita to get the torx screws out and you have to put it a lathe to make sure the shaft is perpendicular to the pump

Dana included a new stator shaft in my kit but I couldn't find anyone local that wanted to deal with it. I also didn't feel comfortable with letting just anyone do the job. So I purchased the bushings, replaced the two end bushings (there's one down in the middle) and called it a day.