I personally would not buy used springs unless I could verify the mileage for sure. Like if a friend had them or something. With that said, my 91 GT had a full Steeda suspension setup on it and it was a very good handling car.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.