The GT3 Seats WILL NOT LOWER YOU IN THE CAR. In fact, because they have a more upright seating position, you will sit higher. You can get the B&K mounts, and those will lower the seat a bit (I don't know how much). However, you will not be able to adjust the seat front to back (no sliders). I went with a Recaro Profi SPG XL and it was about 1.5 inches lower than the stock seat or the GT3 seat. This is with the Recaro slides and the B&K side mounts and adapters. Price is within $50 per seat of the GT3.
Whatever seat you decide on, check out the height of the shoulder harness openings. The GT3 and the Profi SPG XL are the only ones I found that are high enough to prevent spinal compression in an accident. There may be others out there, but I know the Sparco Evo2 and Evo Pro 2000 are not high enough.
Here's more info on what I went through trying to find a seat for track days:
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