I have been looking at four different kits for the four major aftermarket manufactures. Ford Racing, Steeda, Roush, and Saleen.

Ford Racing 2005-07 MUSTANG HANDLING PACK $1299M-2005-FR3
includes:
Dynamic Suspension dampers
Progressive springs with 1.5" drop.
F & R Anti-roll bar kit
Strut tower brace, parallel beam

Steeda
555-2370
'05-'07 Steeda Handling Pak $899.95
Package Includes:
Steeda Sport Springs drop 1 inch front, 1 1/4 inch rear.
Steeda Steel Strut Tower Brace
Steeda Adjustable Front Sway Bar
Steeda Rear Sway Bar w/ Endlinks

Roush
Complete Suspension Kit
2005 - 2007 Mustang $1,468.25
Non-adjustible Struts
Springs
F & R Anti-roll bar kit

Saleen
2005-2006 Saleen Suspension System $799
Part Number: 10-1300-A11503*
Struts and Shocks
Progressive rate Springs, 1.5" drop.
Front only Sway Bar

 

I've got the Ford Racing Handling pack installed on mine. Couldn't be happier. It's a surprisingly great ride for a lowered car and corners like it's on rails.