So I modified a pair of the red, black, and suede STi seats to go in the red SVX and I have to say, they're amazing. They were actually easy to modify, I had to cut both of the rear mounts off, then I slid the inside one foreward till it lined up, and the outside ones I just swapped between the two seats and moved foreward. The unexpected upside is that I gained a bunch of leg room which is great for me at 6'8".
Moral of the story is modifying Impreza seats to fit is actually pretty easy.
The last pic is where the original inside mount is located just for refrence.