Count the number of nubs. They should be visible around the top of the springs. The spacing on my post didn't transfer very well. The 1st 10 digits are the part numbers. The next column is the number of nubs for ID, and then the last column height.

The rears run from 9.5 to 19mm, so the max you can take out is 9.5mm which would reduce ride height about 15 mm.

You may like the back end higher than the front for appearance but if your looking to improve handling you want the back end down as it's the only way to improve camber.