Alpina appears to do a full cosmetic treatment to the interior. Sometimes different colors on the exterior.The last B12 5.7s were done in that shimmery color changing paint.
Different parts may be replaced-See the CF hood with louvers on the 5.7. $6000+ US for that little baby
$5000+ for a copy
Underneath they usually modify the suspension and Supertune the Motor, exaust and transmission.
Then they put a unique serial number on the car. With German TUV certification and blessing.
As far as importation to the US is concerned, Alpina does not exist as a US importer or manufacturer.
The Alpina Z8 was still using the BMW VINs but was treated by Alpina as one of theirs. But BMW was the official manufacturer.
That was how it used to work back in the days of the 2002. They were labeled Alpina 2002s but still had the BMW serial number.