The rear spring is a fixed length
The rear spring perch and top mount are fixed locations
You can’t change the height just with the shock.
You can buy a different length spring with the same Or different rate, Swift makes all sorts of springs in different lengths and rates
Or
You can get the SPL adjustable midlink. I thought you already said you were gonna…?
The SPL mild link has a spring perch that has height adjustment. Just make sure you get the right diameter spring, I think it’s 65mm
From talking to SPL directly, a 6 inch spring is appropriate for almost every one
EDIT;
Look at the pictures
https://www.splparts.com/products/37...mid-links.html