Eaton Detroit Springs
www.eatonsprings.com can fix you up with rear springs made however you like. Pair them up with a Hellwig adj. rate rear swaybar. The Mustang unit should fit,we`ve used them on other Fords and the most we had to do is add or subtract a couple washers from the end link hardware to get everything lined up perfectly.
For the front I`d go with Total Control, we`ve always had very good luck with their parts on clients Mustangs and Falcons. FWIW we carry their full line and have worked with them for years. We`re just now working on getting their parts up on the website. Mark SC&C