I am aware that its larger than my original factory unit. But I believe modifications can be made to make it fit. Like relocating the ESP and fog light buttons and of course widening the hole for which it will be mounted in. I got the unit free from a wrecked 06 ML350. Eventhough the truck was damaged badly. Once I pressed the power button on the command it did come on and work perfectly. I also have the vin from the wrecked ML so I think the command code can be acquired from the dealership. The only problem I believe I will run into is, this unit has two fiber optic wires that I believe runs to the factory amp, my car and amp only has one fiber optic wire. Thanks guys.
I won't comment on the merits of hacking holes in the dashboard of a W163 to accommodate a free head unit from a W164. Each one to their own.
What you need to do though is not think of fiber optics as "wires" because wires traditionally run from one master component or hub to other components in a web like fashion.
The fiber optic cables in the W163 are in fact a "ring". Each component in the ring - for example the head unit, the amp, the CD changer, the telephone interface - are located on a continuous ring made up of several fiber optic cables. So each component has a fiber optic cable coming into it, and another fiber optic cable exiting from it.
Put another way, each component has two fiber optic cables connected to it.
This enables coded signals to be passed around the ring through all of the components and then interpreted or used by the component which the signal was intended for - for example, turn the amp on, or eject the CD from the CD changer.
If any single cable is missing, unplugged or damaged (i.e. the ring is not complete) then the coded signal cannot pass all the way around the ring and thus no components, repeat no components, will work. It follows from this that if the coded signal from a W164 head is not compatible with the coded signal requirements of a W163 amp or CD changer then nothing will work. I do not know if there is a compatibility issue, but I am just making the point.
I think you should study the attached two documents and do some testing before
you hack into your dashboard. Making the unit fit might be the easy part, making it work may not be so easy.