for a street car, they should do fine. they are variable rate (i think)- so they are soft at small displacement but the rate gets stiffer as spring compresses.
not a fan for serious track work because the rear spring rate keeps changing, but they are fine for occasional track use too.
in general terms the 75 & gtv6 use same spring rate. however, because of the dimensions of the chassis (in this case the distance between the lower and upper spring seats), the GTV6 uses a shorter spring than the 75.