I went from a non-Z55 suspension (regular, but cheap struts and keeping the original springs in the front, and cheap coil over shocks and keeping the original springs in the rear) that was installed prior to my purchasing the truck, back to the OEM Z55 suspension using original GM parts whenever possible (air and electric in the rear and electric in the front). Also, the electrical connectors to the struts/shocks were cut off and replaced with resistors on all 4 wheels by the previous owner, and I am still working on restoring the electrical part of this Z55 suspension.
On the front, I changed out the entire strut assembly, including the springs and top bearing caps with new OEM struts and Moog springs (the OEM Z55 springs are no longer manufactured by GM) I also replaced both upper and lower control arms and bushings, including the ball joints, since I was in there and had the front suspension all apart, and one of the ball joint's grease boot was shredded.
On the rear, I replaced the entire shock assemblies, including the springs and air compressor. While the original springs were still there, I decided that the springs had to have some age-related fatigue with 140k miles on them.
One of the great aspects of the Z55 suspension is that your truck automatically levels, with or without a load in the rear, so the truck is always level, and you do not need to go through a leveling mod, just to get the truck to sit and look level at all times.
If you are committed to converting to a non-Z55 suspension, you 'should' be able to replace the front struts with non-Z55 struts for the same model year. Please note that I have not personally confirmed this compatibility, but folks on this Forum can confirm strut part numbers for you. On the rear, you can either: (1) replace the shocks and springs with non-Z55 shocks and springs for the same model year (Z55 springs are softer than non-Z55 springs, as the Z55 suspension has air assist shocks, which help the springs support the load), or (2) replace the shocks with coil over shocks and retain the original springs. As previously noted, you will need to add resistors to the electrical connections at all 4 wheels to fool the truck's computer into thinking that the original Z55 suspension still exists, in order to avoid throwing codes and lighting up your dashboard.
Good luck on whatever direction you decide to go in.