For an 01 Cobra, if you want a 1.5 inch drop, I would suggest either the Ford Racing F springs (made by Eibach for Ford) or the Eibach Pro-Kit springs themselves, which is part # 3590.140.
http://www.stangsuspension.com/store...?idproduct=833 Here are the F springs
http://www.stangsuspension.com/store...?idproduct=910 These are the Eibach springs.
Both have the same spring rating and drop, at about 1.5 inches.
Sincerely,