Honestly the Eibach Pro-Kit lowers a pretty even amount. Around 1.5 inches front and rear.
The Eibach pro-kit has a nice drop vs. the spring rate. It still allows you to get the look you want, without sacrificing ride quality too much.
Shocks & struts are always recommended... Your car will ride better, handle better, and be in good shape for 100k+ miles to come... Without doing the shocks you can be in for a little bit rougher and less "predictable" ride.
CC Plates are also highly recommended. Your front camber will cause inner tire wear with the Eibach Pro-Kit drop.
Here are direct links to the products you mentioned...
Eibach Pro-Kit Springs -
http://www.stangsuspension.com/store...?idCategory=42
Suggested Tokico Shocks & Struts -
http://www.stangsuspension.com/store...?idproduct=938
Suggested StangSuspension.com CC Plates -
http://www.stangsuspension.com/store...?idproduct=478
Sincerely,