Got my Progressive Shocks and springs here .
Use the top link to look up the sizes.
I have the 440AIS series.
Stock length is 12½". For lowering you need the shorter ones and a special lowering kit (listed when you use the fiment link)
Warning: They're not cheap!
There are also the Ikons and others, NewSpeedmaster and BellaCorse sell them too.

A word to the wise is not necessary. It is the stupid ones who need the advice. Pat