You can also install a spacer behind the shackle mount. I have some 3/4" solid steel blocks installed with longer bolts & lock nuts to the frame. I did it on my race car to get the more favorable angle for racing on the shackles (bottom angled towards the back) with my SS springs. I have extra blocks.
I don't remember if the OEM set up has nuts built into the frame or they came with bolts & nuts.
