Correct 2WD has 7.5, as did Granada's, lesser models had 7" diffs (Although some late DOHC 2L had 7.5") the 4x4 beam is just the same as a lesser model, the 2WD beam is different so as to accommodate the bigger diff, so you can't simply just change the diff.

In both Cosworth models they naturally are LSD'S.

Martin