josh...for the s80, the spring u bolts front and rear (and side-to-side) vary, they are not all the same size/pattern.
So I think you are wanting to replace all is that correct? If so, post which rear axle you are going to end up using, the d27 unit or the d44 offset unit. And we need to know if you are going to retain the oem springs and spring pack thickness, and also retaining the oem spring plates?
We just wanna make sure we help ya with the right stuff from the git-go, many folks have hashed these things over so much there is no telling what ya got now! I'm following your build-up thread and I know you are not doing a full-on correct restoration.
Also in this same light, I did some inexpensive upgrades for all this stuff on my own s80 that keeps the oem appearance, provides a slight lift, improves steering feel and return, and really beefs the spring mounting scenario, I can share that with ya if interested, all the pieces for doing that are on the shelf at ihon. At this point I'm retaining the oem springs, though in the future I'll most likely add one additional leaf to each spring.