[Stephen Watson]

I just came across this today searching for other stuff and thought I'd address some questions for posterity. Obviously there's a date gap but some people actually do search...
ORD is not selling Alcan springs. This is a constant source of confusion and we don't know what to do to clear it up. Alcan builds Alcan brand springs from a spring shop in Grand Junction CO. ORD buys springs built to ORD's specifications from the same spring shop in Grand Junction. Not alcan specs and you can't order ORD springs from Alcan. We work closely with them on a lot of suspension projects but our leaves are not the same.

As to the question of why the shackle flip over 3" of lift on a '72 back truck: An actual soft spring for these trucks (not a "soft ride" or "ezride", etc but one that actually rides nice) has to have a deeper free arch because it's going to compress more under the weight of the truck. Standard stuff in the way springs work. A '72 truck requires a little more rear spring arch than Square. Add these factors and you end up with a deeply arched spring in the unloaded state. This was mentioned by someone in this thread, they thought their springs looked like a much higher lift. This is common enough that we address it in our instruction summary page.
When leaves have a deep arch, the eyes pull together making them require preload to install. Preloading leaves involves spreading the leaf eyes apart to reach the shackle eye and is unusual in leaf spring world making it seem wrong in addition to being really awkward. We generally try to avoid this.
The solution to making the spring reach the shackle is to use a longer shackle that will lay down horizontal. This works in many applications but the 67-72 trucks have a bed rib above the shackle hanger and the longer shackle hits it. So no long shackle for you. At this point, we need to flatten the spring arch and the shackle flip is a great way to get you into a flatter spring. As others have said, the flip does not introduce any inherent handling or load carrying problems as evidenced by the later model 1-ton trucks running this system.

The reason a regular "lift kit" spring can give you up to even 8" of lift with the tension shackle is that they don't really move because they're really stiff.

There is one new part that alters the equation a little and that's our new tension shackle hanger. This piece drops the shackle mount point and lets you run our 6" long shackles with no change in ride height. This piece allows a 4" lift with the tension shackle system on the early trucks. We still have to do a shackle flip on a lift over 4".

We've also been fighting a reputation as "only for rock crawling" for a long time. We like using our stuff offroad but we have a very firm grasp on making these trucks work on road in both ride and handling and that's really been enhanced by making them ride and handle offroad.