Here a couple links that will help you out. I just used them to replace the shocks on my 56. Make sure the shocks do not bottom before the suspension. Remember to subtract 1 1/4" from the measured suspension distance if there are stud mounts on both ends of your shocks. Mikehttp://carvin.net/jj/shockabsorbermeasurement.pdf
http://www.monroe.com/assets/downloads/english/08_MountingLengthSheet.pdf