i bought them from kaiser brake here in eugene. they make some parts of springs and i believe they get parts for them from portland.
i have a soa, but the springs were too long and not put together correctly. the arc was too severe which made the back end too high.
i wanted 2 or3 inches taken out of the lift, they are made for 2400 lbs total weight and most importantly, they are softly sprung. dezert prerunning.
the top half leaf helps with anti-wrap. cory does this with a lot of his springs.
having them made covered all my concerns. these are a one off spring.
hope this helps, dave