After I put the Recaro's in my car (both Facelift), I put my old half leather seats into my mums non facelift MK3 Mondeo Ghia.
Her non facelift front passenger seat had a load sensor on the seat cusion which told the ecu whether anyone was sitting in the passenger seat for the airbag system.
The drivers seat had an extra bracket with a sensor on to tell the ecu how far forward or back the seat was positioned. Again, for the airbag system I think.
It just made the job a lot longer as I had to take bits from out of the old seats and fit them in the new ones.
Thinking about it, you should be ok with an 04 car as I think your car doesn't have the extra sensors to worry about.
I would still try and buy a facelift ST220 interior tho, just to be on the safe side.

Regards,

Nick