This experience comes from my days racing.  The way we checked springs
then required three measurements; spring height, diameter, and spring
rate.  The height and diameter you can measure with a tape.  The spring
rate need to be done on a spring compressor.  This device has a guage on
it to tell the ft. lbs. of force of the spring under compression.  
There is a formula for the amount of spring rate you need for you car. 
Unfortunately I don't have it handy.
Alternatively you can change springs in and out until you find two that
work well together.
        Regards,
        Tom
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