[mylesdw]

...just occurred to me: although the lsd/open casings are the same I have heard that there are two styles of pinion shaft and they need a housing to match. I am not sure of the accuracy of this info, but I believe there are two different ways in which the shimming of the pinion is done, one with a collapsable spacer and the other with shims and for this the casing and the pinion must be of the same type. This may be complete nonsense, it is only hearsay...