Alright, your truck is not the same as a 2 wheel drive. They probably got confused about edges being the same as 4x4. They do not have drop kits for 4x4. To drop if for free take out the rear blocks and losen the torsion bars.
Take out your rear blocks and unscrew the torsion adjustor bolt all the way removing them (wouldnt want them to snag anything and break off) and that is about as low as a 4x4 can safely go should give u about a 2"-2" drop.
If thats still not low enough get in touch with TippnOver he did the axle + torsion key flip giving u about a 5"-5" drop.