Unless the suburban you are looking at is pristine, wait until you find a suburban with the clam shell tail gate. The cost to convert will be around a thousand dollars and lots of work.
Things necessary to convert from barn doors to clam shell:
Removal of barn doors:
Door checks,
Hinges
Installation of clam shell tail gate and upper lift gate includes:
Modify the upper header panel to accept lift gate hinges (two styles were available) Install hinges.
Mount lift gate and lift gate props. (drilling may be necessary, nuts may need to be installed)
Install cable guides on both sides of body. (you may have to drill body panel to install)
Fabricate and install lower tail gate mounts underneath the rear body sill.
Cut out holes for bottom hinges in outside sill panel.
Install cable retractors and cables.
Install tail light rod to tail light and wire light
Adjust tail gate and lift gate for proper fit..
Install weather stripping
Install rubber knock out plugs in old barn door hinge location.
Probably a few more steps but this is the gist of it.
