As both these model-years concern the same series of Focus, there would definitely be some interchangeability. Body panels should interchange readily (provided you don't try to fit the hatchback from a five-door to the boot of a four-door) and many interior fittings would also be able to be swapped (provided the interior colour and trim materials of the two cars matched).

Mechanically, however, you need to be a bit more careful. Obviously, there would be major differences between the driveline of the diesel version and the more common petrol model, but there will likely be differences to driveshafts and all sorts of components when you compare a manual Focus to an automatic one. Different trim levels can also cause interchangeability problems in terms of a base-model car not having the electrical wiring to support the convenience equipment of the upmarket version. Things like the power windows in the rear of a Focus Ghia, for instance, will cause problems in the base-model CL which relied on manual rear windows.

It will all depend on when in 2005 the Focus in question was built. Ford changed from the Mk1 Focus (LR model) to the all-new Mk2 Focus (LS model) in April of that year, so an early-build car will not be the same as the 2009 model, although a later-2005 one might be.

These two versions of the Focus were built on different wheelbases and platforms, so there may not be too much interchangeability. Certainly the bodies were quite different, so panels and interiors won't be interchangeable at all. Even the steering systems were different model-to-model. The Mk1 used conventional power-steering, while the Mk 2 switched to electro-hydraulic power-steering.

The compliance plate under the bonnet will tell you all you need to know about the car's build date. Visually, the earlier car had a much more angular style at the front with almost triangular headlights, while the later car was more upright and conventional looking.

Although both the Ford Focus from 2004 and 2009 were both offered with a two-litre petrol engine, those engines were actually different in terms of their mechanical specification. With that in mid, it’s very unlikely that the clutch from the earlier car would be compatible with the later version. A quick search also revealed that the replacement clutch kits for each version of the Focus you’re dealing with carry a different part number which is a pretty good indication that there are differences between the two.