Which Diff fits?

Just done a quick search, and couldn't find an answer:

Will TDCi differentials fit earlier (TD5) vehicles?... I assume they are 24 spline and same 3.54:1 ratio.

Still searching...

From what I can see diffs from 300TDi onwards have 24 splines and are basically all the same (Rover type)... does anyone concurr?

My caution is that some diff guards specify 'post-2007'... was there a change to the axle casing rather than the diff itself at this point?