Replacing the stock coil springs is not required, and is generally unnecessary. The only OEM component that you may want to consider swapping out is the upper strut mount and bearing, but only if you have a lot of miles on your truck. The only springs that available on the aftermarket are the Eibach Pro-Lift Springs, which add 2.7" of ride height at the lowest perch setting, which may be a good or a bad thing, depending on what you're going for.