All late BC box's have the bigger bearings mate, you can tell by the 'core plug' at the end of the main shaft on the casing.
CTS just machine out the older casing to take the bigger bearings if they dont have any of the later ones.
But it isnt the bearings that fail mostly it's teeth stripping off the input shafts (hence the disclaimer on the receipt), the gearbox wil last longer with bigger bearings if it makes it to the point of bearing failure that is! lol