The 722.0, 722.1 transmissions used three different diameters B2 piston during its evolution.

The first was 75 mm then in the late 70s it was 88mm and finally and 92 mm. How deep is the worn section in the bore? What does it feel like when you move your finger over it?

To determine if the case is salvageable insert a new ring into the bore, in an unworn area measure the end gap., know place the ring were the wear is , a reading of more .012’ means replace the case. If you can’t find one look into the possibility of sleeving the bore and using the 88mm piston, or borering / power honing the bore and using a machined early or late 722.3 B2 piston or a 772.4 piston.