The auto transmission is a Ford 4F27E and there are 4 id tags for 00-04
The SPI tranny is a id 1S4P-CA , this has a 3.69 1st gear
the Zetec ones are id XS4P-DF and XS4P-DA Im not sure the difference between these they both have 1st gear 3.90 and are for the zetec. one says for 00-01 and the other is for 01-03 on the ford printout I looked at.
You can use an SPI tranny on a Zetec I am doing it now.
You need to use the Zetec tranny harness though because of the Flywheel position sensor that is on the Zetec and not on the SPI.
Search Ebay for brand new OEM XS4P-DF and XS4P-DA for 600-900 bucks.
how well has the SPI 1S4P-CA functioned in your Focus? Have you had any problems? Did you have to do any modifications or just remove the Zetec Transmission and install the SPI 1S4P-CA and connect everything back up?