Yeah.....seen this on another caddy site. Some euro states require the orange turn signal lamp. If your in GB and import a Germany car you basically have to swap the taillights. The orange export lamps are very, very rare and are about $200US each.
Here is a link to a picture of the export lamps. They have the orange corner lamps. They also do not have the horizonal painted feature lines that every one in the US is use to.
http://www.movit.de/images/sts11.jpg
As for the conversion. The export cars do use a export only harness. Your best best would be to get a Helm issued factory service manual. It does have the export harness diagram. The other books available are considered to be a joke.
The Helm books can often be found on eBay. Search for 'cadillac seville'. The can also be bought at
www.helminc.com . They are worth every penny.
Logan