I know this is a slightly old post but I just had Spring Align in Palatine put a nice set of full length add a leafs on the front of my X which raised it up 2" and restored the front end ride. Installation included new U bolts and hardware along with spring spacer and loop to make sure they stays put. Springs are rated for 700 lbs total capacity so its a nice addition since the stock X springs are very weak in rating compared to the F250 and F350 SRL. The front you to sag, bounce a lot, and even dip when braking. Not anymore thanks to Charlie at Spring Align!
They have 3 shops, Palatine, Chicago and Northlake. My friend had them replace the rear springs completely on his F350 that had 220K on them and he's the one referred me since he was happy with their price and service. All they do is Heavy duty trucks so you wont have a mustang mechanic working on your truck. Hope this helps. Spring Align