KZ400 Speedometer swapping

Ok, I have searched the archives previously for several hours, without success, so I ask:

- Is it possible to swap the MPH/KPH speedometers on a Kawasaki Kz400-D3?
- Is it possible, for example, to mount the speedometer of a KZ250 (KPH)?

In my thinking (free thinking) I understand that the difference is made by the gearbox and not the speedometer, which will simply show the laps that it sends in MPH or KPH.

They are expensive pieces, and buying something that does not work would be a headache.

In terms of speedometer function, yes it will work. However, there can be quite a few other differences depending on the exact year and model. I am not real familiar with the 250, but on other models the speedometer may have the high beam indicator, brake light out indicator, oil pressure indicator, or most any combination of these, or none off them. Some larger models had a colored trim ring under the glass, around the face. Also, some larger displacement bikes used an electronic rather than cable-driven speedometer.
One way to eliminate some of this is to go to a site like Partzilla.com and look up your exact year and model. Find the diagram for the meters and click on the part number. A bit down the next page there is a Fitment chart that shows all the models that use that exact speedometer. 
CMSNL.com and Kawasaki.com have the same information, though the Kawasaki site is not very user friendly.

Here is a list of models that used the same kph speedometer as the KZ400 D3
www.partzilla.com/product/kawasaki/25005...c354d6ae6287770c46b0

The speedometer may not fit the meter bracket correctly.  The 250D1 has some of the same meter parts as some 400/440 models.  At Partzilla click the part number for the cross-reference.  You could compare your stuff visually & ask the seller for the mounting stud spacing on the 250 speedo.