I keep a few old input shafts in my shop drawer. I have a 10, a 26 and a 14 spline.
I'll use an old shaft to check for binding BEFORE I attempt installing a tranny. It's easy enough to verify that it fits inside the pilot bushing by using it the same way you use the plastic clutch alignment tool that comes with the clutch kit. You can also verify that it has the same diameter as your transmission pilot tip with a simple caliper.
