? If you didn't know a springs rate is there a way to find it the same way manufactures have it listed?

Depending if the springs are coils or leaves, there are formulas for calc'ing out spring rates. Right click / copy, the image below, then enlarge it in a image viewer to read the fine print....

http://www.imagestation.com/picture/sraid19/pbf31e61bc1716baf1c2de51e79529b1d/fdc2a247.jpg