so why not buy stock springs???  do you want to lower the car?

Why? If you do that you get the car handling and sitting exactly the same
way it does as stock but with the potential problem of the springs not
lasting as well as the OEM ones.

If you are trying to save money buy buying pattern springs then why bother
to save so little? It could be that the reason you haven't found any specs
are that the spring manufacturers have decided the market is too small to
bother with (for the return on investment) and so stick with lower ride
height/stiffer springs instead as that's what most people expect from
aftermarket springs.

With suspension unless you are modifying it in a specific way replace with
OEM parts every time and always do both sides of the car simultaneously e.g.
if you have a broken spring then change both sides on that axle, same with
dampers or struts.

Chris