8 3/4 pinion splines

I'm guessing that the coarse spline pinions tend to be aftermarket, which may be cheaper to make. But I've seen it with other housings also. It usually says which spline it is in the sales ad.
All 741 pinion are suppose be 1 3/8 with a 29 spline Pinion according to every parts manufacturer I've found. That's why I can't figure this one out.