We've had a Cape York, Explorer Extreme since 2005, my mate, ...... who was in the 4x4 supension industry most of his life, took one of our springs from our camper to try and figure out what they were from, but allas, no joy.
The head office, at Cape York Campers in Cairns ( Ahern Metal Indurtries ), once told me that they had their own coils wound especially for their campers.
The closest my mate could find as a match were Landrover Defender coils.
How that's of some help !
Cheers
John K