I want to see some numbers on my stock ones and do some comparisons. What tool do I use and where do I get it?

 

If you're ghetto... you can do this...

Get a wooden plank, and set it on top of the spring. Sit on the spring. Weigh yourself. Have a friend measure how much the spring moves after you set your entire body weight on it.

Do a proportion to back out how many pound/inches your springs are. Remember the cross multiply and divide y'all learned in high school? And I bet ya thought you'd never have to use it...