This is from ARB head locker engineer confirming this :-

Hi Frank,

I can see what you are trying to do (I think) but there may be some complications.

Here are some notes that you may or may not have considered:

1 Although the ring gear IDÆs are identical the bolts in the 9.5ö are larger, so you would need to make up sleeves for your 9ö bolts to suit a 9.5ö diff.

2 The bearing ID of the 9.5ö diff is MUCH larger than the 9ö, and so you would probably need to consider machining the bearing journal of the locker.

3 The RD154 has a different seal housing system than our RD46 diff, and it fits underneath the bearing cap. This makes it specific to the 9.5ö bearing size, so you would have to work something out for the 9ö. We might have something else off the shelf that would work (a different seal housing that might suit the 9ö bearing) but I couldnÆt guaranty it.