There are essentially 3 types of box
Higher geared diff:
Ph1
Lower geared diff:
Early Ph2 or Ph2 Cup with speedo drive
Ph2 non speedo drive (172 or 182)
If you have a non speedo drive, you can fit any of the above.
If you have a speedo drive (ph1, early ph2, ph2 cup) then you have to fit either a ph1 or early ph2
If you fit a speedo drive to a non speedo drive car, you need to add the actual speedo sender to the box to blank it off (doesnt need to be a working one but they are only 13 quid new) or make some form of blank.