Hi, I didn't want to drill the shaft in the box, so I made a small collar, and installed it onto the steering shaft up against the mount for the steering shaft bearing. The bearing bolts in to the cross tube that supports it bearing.The collar keeps the steering shaft from coming out because it is against the bearing. Look at the picture,(up above the tranny output, right above the bolt ) you can see the collar welded to the steering shaft, keeping it engaged onto the splined input shaft on the steering box.
Hope this helps,
Roger
You could also use a split collar (industrial supply place) for the diameter of your steering shaft, if you don't want to weld to your steering shaft.