So after all it seems that Arnott actually has two different options available for E53, SE and sport.
On BMW diagrams the two axle air suspension has always the same rear air spring regardless if sport or not. And that version is the SE/normal version on single axle air suspension. Single axle air suspension only has a separate sport version rear air spring. And this is what you need if you want to keep things the same.
Single axle air suspension Sport on Arnott options: A-2503 and A-2504.
https://arnott.mycarparts.com/applications/576