Off-roaders have been modifying leaf suspensions practically since the leaf spring was first used on horse-drawn carts. The methods to improve ground clearance on vehicles with this simple "carriage spring" suspension have varied little over the years, but hundreds of years of development have made one thing clear: leaf spring lifts should be approached systematically, without relying on any one method to gain altitude.
An axle flip is the simplest and most basic lift modification for most leaf-spring suspensions. More than half of all Hotchkiss leaf spring suspensions utilize an axle-over configuration which, as the name suggests, places the axle on top of the leaf spring pack. Removing the axle and welding a flat "spring perch" to the top allows you to place the axle beneath the spring, which can net anywhere from 4 to 8 inches of lift (depending on the thickness of the axle tube and spring pack). An axle flip should be the primary lifting device, as it necessitates little or no change in suspension geometry.
The leaf spring package is composed of many individual spring strips, or leafs, held together by strong steel straps. Disassembling the spring pack and adding extra strips can easily net an additional inch or i1-1/2 inches of lift without drastically changing suspension geometry or negatively affecting vehicle ride quality. Junkyard engineers will most often use leafs from another vehicle's spring pack; it's a good approach, provided that the added leafs aren't any narrower than the truck's stock leafs. This modification should be considered a "stage 2" upgrade, or "stage 1" if your truck already utilizes an underslung axle.
There are three basic types of shackle lifts: a flip (similar in concept to an axle flip, used for applications that use upward-facing shackles); longer shackles; and shackle relocation. Shackle flips requiring repositioning of the shackle mount can be a bit complicated, and are a bit unsafe without using a pre-engineered kit. Longer shackles are a good option, but keep lift within and inch or two; overly long spring shackles effectively lower the spring rate and can make for a tippy and dangerous ride. This is doubly true for asymmetrical shackle setups that use utilize a direct frame mounted leaf spring on one side and a shackle on the other.
Shackle relocation (redrilling the frame and moving the shackle mount lower to the ground) offers perhaps the best compromise between lift and ideal suspension geometry. This method can yield several inches of lift, but you'll want to strengthen the frame below the bolt hole with a 3-inch-high/frame-width section of rectangular steel stock boxed in on either side with some 1/8-inch plate steel. A shackle relocation lift will lower the truck's effective roll center a little, causing a bit more body roll, but not so much that it can't be compensated for by some additional spring leafs.
A note on shackle angle: No matter what type of leaf spring lift you choose to employ, always keep your shackle angle as close to a 90-degree angle to the leaf spring's horizontal axle as possible. Extreme shackle angles will lead to poor handling and limited suspension flex.
