[SCOTI]

Like jrpontiac indicated, a flip-kit can be done on the cheap by adding (welding) new leaf mounting pads under the axle tube vs. on top & using fresh/new U-bolts/nuts (don't re-use U-bolt hardware; you can re-use the original plates). But, you'll get more than 6" of drop (closer to 8" depending on how thick the spring pack is). You would need to source the pads & U-bolts for the correct OD of your axle tubes.

The shackles/hangers will get you 4" drop. You could remove some leafs to play around w/additional drop.

There is also another possibility that doesn't require welding but would require some modification (cutting, trimming, drilling, & measuring because you won't have specific instructions). You could use a 98-00 3/4 ton 8-lug flip/c-notch kit. They're similar in design. The axle tube OD should be the same (14bolt GM housings). The main difference is in the frame-rail profile but the 98-00 c-notch could be trimmed to fit where necessary.