Thats what I started with on my Mustang.
The 1996 Mustang has rates of 400-500#. Get springs that are 10% stiffer (like 440-550#), and you will be pleasantly surprised with the nice ride and improved handling.
------------------
Darius Rudis
Roadracer: Home built t-arm/panhard suspension powered by an S-trimmed motor :-)
My Mustang Page