What spring rate are you guys using for rear coilovers? There's so many options I'm not sure....

 

As an engineer I typically don't do this (I'd rather have the calculations to support the answer), but I got mine from Jim Weimer Rod Garage. I asked them how they specify the rating, and he told me that it's basically obtained knowledge over the years. So, if you don't get a direct answer, maybe you could call these folks up.

Jim Weimer Rod Garage - Rear End Components - Quality Universal Triangulated 4 Link Kit, Parallel 4 Bar Kit, Pan Hard Bars, Coil Over Shocks, Parallel Leaf Spring Kit, 9" Ford Rear End