There have been so many part number changes for the rear axle beam, that it's impossible to tell from the parts catalogue if any of them are interchangeable.
The MW (estate) versions may be different because the rear shock absorbers are mounted at an angle, whereas the saloon versions are mounted vertically.
At some point, there was a modification to the handbrake cables mounting brackets on the axle. There was also a modification to the rear ABS sensors cables mounting brackets. You could probably improvise around both of these issues.
For both saloon and estate versions, there was a part number for cars with original Xenon HID headlamps, and a different part number for cars without HIDs. The only difference was a bracket welded on axles for cars with HIDs to mount the rear levelling sensor. You could obviously fit an axle with the bracket to a car without HIDs, or make and fit a bracket to an axle without one if your car has HIDs.
The part number you posted (51795328) is shown in the parts catalogue as suitable for the 2004 model year Stilo MW without HID headlamps.
I don't know if there are any dimensional differences between any of the axles.
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