4 speed identification

What should the diameter of the retainer be for a 23-spline shaft?

By the way, I found a neat way to count splines (new to me, anyway): Put a light coat of grease, or something that can make a definitive mark on paper, on the outer surface of the splines, then wrap a piece of paper around the shaft. Count the marks. Mine was found to be 23. Definitely not 18.
it would be nice to see you start your own thread here on the 4 speed part of the forum on that tranny you're going to get?