Guys, I done this write-up over on GMFS but I've been PMed by a few members on this site about my lowering kit. I know this site is more engine related but I feel that this write-up would be a great addition to it as well.

WARNING: THIS IS FOR NBS TRUCKS. SOME OF THE CONCEPTS EXPLAINED REMAIN TRUE FOR ALL VEHICLES; HOWEVER, THE PARTS FOR OTHER APPLICATIONS VARY!

2/4
As far as I'm concerned, most 2/4 kits are all relatively the same. The only one I've personally used however is Belltech.

For the front:
Depending on the cash that you have to spend, you have a couple options to lower the front. Most commonly for a 2" drop, drop coils are used. Over time these coils will settle approximately another 1/4"-1/2." Perfect alignment should still be able to be achieved.

Also, another option to use would be a McGaughy's 2" drop spindle. NOTE:McGaughy's makes two different spindles. There is a 16"+ spindle that will work on all wheels 16" and larger. However, these 16"+ spindles will decrease your turning radius. The better of the option would be to run their 17"+ spindles. These spindles can be used on all wheels 17" and larger. Also note, if you are running 17" wheels, you'll have to grind down the stud on your balljoint directly below the nut & cotter pin on it. Although this doesn't sound ideal, these spindles retain a factory-like ride and also keep the stock turning radius. Belltech also makes spindles. Their first design was junk from what I recall; however, they did revise the design and I believe the new design is a good design.

Back:To achieve a 4" drop in the back, drop shackles and hangers can be installed. Note that with these hangers (only on RCs and ECs. CCs hangers are welded to the frame) you'll have to remove the old hangers that are riveted to the frame. This is most commonly done by cuting a slot in the rivet and using an air chisel to bust the rivet from the frame.

Also lowering leafs can be used. These will affect towing capacity and leave the ride much spongier in the rear.

4/6

Front: When I was looking into a 4/6, I found myself drawn towards the DJM 4/6 kit that consisted of 4" LCA's and a flip kit for a rear. I am currently running this on the truck now. The only complaint with the DJM LCA's is that the alignment cannot be perfectly corrected without the use of Upper control arms. My alignment is however 1* from being perfectly straight. Also, with the LCA's, some complain of bumpsteer; however, I do not have this. I wouldn't say don't run the LCA's but I would be aware of these minor issues. Also, some say you can use factory UCA's and flip them upside down and get more alignment from them. I have not personally tried this.

Another option for 4" of drop in the front is to use McGaughy's 2" drop spindles and a 2" coil spring. Both of these are discussed above under the 2/4 section. If I were to do it over again, this is the route I would take.

For the rear, the 6" drop is commonly acheived by a flip kit. The flip kit relocates the rear axle on top of the leaf springs. For an extended cab, you'll need to get the carrier bearing as well since you have a 2 piece drive shaft. You can also use drop shackles for 8" of drop.

Also, you can use a combination of drop hangers, lowering leafs, and drop shackles to achieve the 6" in the back but the flip kit is BY FAR the easiest method.

NOTE: With any more than 4" of drop in the rear you will want to cnotch the chassis, allowing the axle more room to travel.

Also here are the part numbers for the Doetsch Tech shocks to be used with the 4/6:
4080G for the front.
Use 4173G for left side & 4241G for the right side for the back.

Note: Its often a common misconception that Pacesetter & Dynatech LT's and ORY will drag below the frame rails. This is negative as they can be ran with any of these setups including 'bags.

I've probably forgot some things that may be relevent. Anyone else feel free to add more and I'll put it in the first post