Here are the measurements for Ridetech coilovers. It looks like the 6.9 will work for you based on the measurements you provided.
Stroke......Compressed......Ride Height......Extended......Spring Length
2.9"..............8.73".............10.5"......... .....11.63"............8"
3.6"..............9.43".............11.5"......... .....13.03"............8"
4.1"............10.13".............12.5".......... ....14.23"...........10"
5.2"............11.23".............14.5".......... ....16.43"...........12"
6.3"............12.33".............16"............ .....18.63"...........14"
6.9"............13.13".............17.25"......... ....20.03"...........14"
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*Check your other thread regarding shock lengths. Josh provided some good info regarding the Ridetech coilover conversion kit.