I recently bought an 86GT that apparently has aftermarket springs in it. For the life of me I can't figure out what they are although I am leaning towards the FMS C springs. They are extremely stiff, so much so that if I push down on either the front or rear of the car I can only move it ~1/4". There is zero body roll and the ride is harsh to say the least. I have nothing to compare to but I'd say the ride height is very near stock. Here are some pictures to help....
Front:
Rear:
