H&R and Eibach are good spring choices. If you want to go high dollar, get a set of Tein coilovers. You could also get the Omnipower coilovers for cheaper, but the shocks are nonadjustable.
__________________
2015 Ford Mustang GT Fastback - Ingot Silver - 6M - Performance Package - Gibson Catback, JLT CAI, FR 47lb injectors, BAMA E85 tune, Eibach Sportline, BMR wheel hop kit, UPR oil separator, Steeda shifter bushing/bracket
Team B.O.B.® - Ballaz on a Budget