If i lie a ruler flat on the tyre tread and then measure from that to the arch it is 11mm both front and rear, im not sure what it was before but you can compare yours to that.
The coilover kit as you can see from the pics above includes the spring and damper and is height adjustable. This is all tuned to match each other. Springs are just springs, you will have no adjustment in height and you'll be running an uprated spring without an uprated damper which can prematurely wear out your dampers.
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