I got new springs for my '51 1/2 ton and I couldn't have been more pleased. Just like the originals, made in USA, and had the bushings already fitted. Oh, and they were about 1/2 the cost of getting the originals re-arched.
Here is a link to SDTrucksprings:
Springs for K10 Can't comment on the K10 springs but the springs for an AD were OK.
Kurt