There are three parts that must align for the OD to "slip" onto the trans shaft.

The lobe of the pump cam on the trans shaft should point down.

To align the splines of the cone clutch and one way clutch need the crewdriver trick or a clutch alignment tool of correct size.

The one way clutch is the only part that will move of the two. It will only move only one way and it takes a bit of effort to control how much since you are working at the bottom of a deep hole. After the two splined parts are alighned, any movement of the rear flange will shift their relative position.

Try to keep from banging or moving the flange as you slide it forward.

Putting the OD back on the tranny shaft requires patience and a little bit of luck.

Duane