My wife was kind enough to get me a Ground Control coilover kit for Christmas. Thanks Tracie! These are photos of the conversion of my existing KYB AGX struts with the kit.
The conversion went quite well, the only semi-difficult part was the optional step I took -- cutting off the old spring perches. Tire clearance is a big issue with the Impreza, so I wanted to remove as much of the old spring perch as I could. With the help of my father-in-law, his garage, and his die-grinder, we managed to get it done relatively easily. A die grinder was used because it was too hard to safely hold the strut on the band saw.
The photos in the top row show a strut with the stock perch, and the extremely precise mark we made with a Sharpie to aid the perch removal process.
The photos in the bottom row show the front struts after the conversion.
With the perches removed and the camber plates, they look just like you'd expect a "real coilover" would. They also perform quite well, although the 400lb spring rate dictates that this car is probably no longer suitable for rallycross.
The "after" photos are shown with the perches in their highest position. After installation on the car and some testing, they ended up at a bit above their lowest setting. The car is approximately .75" lower than stock, which seems about perfect. This is with 8" 400lb springs -- spring length and rate affect the available height adjustment dramatically, so be sure you know what you're getting when you order.