The first hurdle to your plan that I can see is the 6 spd does not have a Vss (vehicle speed sensor) instead it gets this information from the wheel speed sensors via the abs ecu using the data bus (Can).

Second, the ecu wiring loom is fairly well integrated into the car and does not separate as easy as a focus.

I am not sure on the dash but I suspect apart from the lack of vss it will be fine.

Ttv list there single mass flywheel for both the 5 and 6spd so clutch should be easy.

My opinion for what it's worth is any mk3 mondeo needing any work with the miles yours has is an economic wright off. But if you go for it they aren't that hard to wire up.

This is an st220