I'm a couple of weeks from getting them out. Will post my measurements. According to the manual the free unloaded length is 17.48 inches. The second part of specifying a spring is the spring constant. At a load of 1300 +/- 25 pounds, this spring should compress to 10.31 inches. Free length can be the same but have completely different performance.
My front springs were very close to the specs in the manual. We'll see how the rears look.