I'd personally do the Eibach R1 full front and rear kit with MM CC plates and the MM adapter kit for mounting the Eibach R1 kit to their CC plates.
All that said, you don't actually need coilovers unless you need the adjustability. A good set of springs and shocks and struts is totally fine if all you want to do is lower it.
You will want CC plates regardless.
2000 Mustang GT Steeda build #48. Bolt ons, suspension, Novi 2000.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.