The rear arms are different as the cosworth versions have spherical bearings fitted where as the xr4x4 used rubber only - they are though physically the same - so not a problem if you are planning on poly bushing them.

The rear props are the same, its the 2wd ones which are thicker.

The casings of the 2 litre post 1990 MT75 is the same as a cosworth but the ratios are different, where as the ratios are the same as a cosworth on the 2.9 but the case is different.

The diffs on the 2 litre are 3.9 but 3.6 on the 2.9 ( same as cosworth)

The rear hubs/ bearing carrier are smaller on the xr as they use a smaller disc but the calipers are the same as 2wd cosworth

rear shafts are the same, as is the beam, but the arb is thinner

Front hubs wont allow cosworth 4x4 discs and calipers to be fitted and the rack has a bigger turning circle

mot failure 2 litre xr4x4 sell for around £200 but contain over £600 worth of usable spares so make a good donor for a cosworth project