I'll what I can here.
I ordered the "Mustang handling package" for my GT after finding it to be in my budget, and my level of useage. It's basically a BULLIT or MACH1 suspension(((2 shocks, 2 struts(all Tockico), 4 springs(600fr/250rr), 2 swaybars(lighter/hollow)for 440 shipped))).
I tried using a set of C-springs with this kit, but it did put the front a lil' lower than I expected. When I replaced the springs this time, I used the springs in the "kit" but I did not use any of the rubber isolators. I found this to be right about where I wanted it. I can almost get my fist inbetween the tire and the fender well.
As for the Handling compared to my old setup(Eibach ProKits with stock everything else that was replaced), the car feels GREAT! It does ride a lil' more rough, but I really hope it picks up 1/2 a second or maybe a lil more this season for autox. The car feels very solid, and very predictable in the corners now.
I do feel that the front could stand to be just SLIGHTLY lower in the front, and I have sale pending on some Steeda X2 balljoints at the moment. If I do not use the provided spring spacer with them, it should give me a "pinky finger's width" drop in the front I need.
I purchased the parts from www.stangstore.com
if you want to take a look. Was surprisingly shocked as I ordered the parts at 3pm on a Friday, and my junk arrived by 5pm Monday. Just regular shipping, nothing special. All parts arrived perfect.
Good luck in your choice. I personally don't like "SLAMMED MUSTANGS" so my opinions may be biased.