Thanks Marc.
Actually I am not sure where either of them came from really (ebay)
But it is a 7.5 diff and it also seems to be a 7.5 beam. The width between the top bolt seems fine. It's a bit lower down where the problem is, right in the middle of the webbed area in this pic. It could esily be cut away I think, but the question is whether to cut the diff or the beam. I'd guess the beam since that can be welded back together easily. - just seeking advice though.....