Fire some pics up of everything if you can.

But as Dojj says, there is 3 variations for the Mondeo Mk3 and all have different applications due to stereo design/shape used by Ford.

Also, if you google Double DIN fitting for mondeo mk3 etc you will get loads of threads on TalkFord and ST Drivers etc of other lads who had issues and had to cut or faff about with fascias etc, some recommend buying a universal cage but cant remember the exact dimensions off my head.