Chicky is actually spot on
Upgrading the shocks by themselves will make a huge difference to the handling and help smooth out the ride on the single cab. As the GLX has HD suspension fitted, it already sits about 1" higher than standard. The single cab is also lighter than the dual cab GLX so that 1" is actually a bit higher. A lot of our customers with these vehicles have been happy with the original ride height and have just changed the shocks to improve the handling.
Our front struts are also designed with an adjustable height coil seat. This is great for the single cab GLX as you can reuse the original coil with a 10mm collar to regain the height lost by fitting extra accessories (or to gain a slight lift).