xc and xd rear springs

Hi.
I put the lower xc falcon rear springs in my xd falcon.The length is the same but the arc is not
the same.Lower xc falcon rear springs sat my xd
at the xd standard height.
I went to the lovells spring site.I found this.
xc falcon
lower lower heary duty cargo/lpg
45-65mm 25-40mm standard heght raise
super low sport low std hgt 20-25mm

xc fls-il fls-ls fls-lr fls-lhd

xd fls-il fls-ls fls-lr
look at the part number