Anybody thought of plain old simple leaf springs??
They are Stable and have the ability to flex great if done properly.
Yes, for years.
The 80 gets its stability from the front end design. Which is why if you 3 link you may not like it. A 3 link is not an inherent stability problem when converting from a four link suspension - all you are doing is removing one upper mount, which controls the position of the pinion. So if your suspension was already designed around a coil sprung four link, like a Jeep, a 3-link is not altering suspension design per se: it is removing a redundant link.
So my thought on wanting to free up the front end is that you need to stabilize the rear, and given that 80 series coil springs are so designed around rear weight load bearing (the whole endless stinkbug discussion), it could be that converting the 80 rear to leafs would be a natural transfer of suspension stability to the rear along with the load bearing properties of leaf springs.
Now if you take a good look at the 80 series frame, it curves up right after the point you would mount a leaf spring, making it well set up for a shackle mount and a relatively flat leaf spring. Just eyeballing it, I think you would get about 6" of lift with what would be a flat spring and therefore essentially stock suspension dynamics including roll axis. Add an anti-wrap bar and you are good.
So now that we have cared for stability and load bearing with what is probably a cheap 63" Chevy spring (conversion paid for by selling all of your aftermarket rear links and coils
) and created a lot of lift height within that stability we can now use a mid-arm (about 22") design to 3-link the front in an overall design where the front end does not have so much responsibility for stability and can be freed up to really flex.
The mid arm design moves the mount forward to not far from the back of a 37" tire, so you are eliminating one of the major compromises of long radius arms: clearance.
Yes, people will point out that this is a Jeep Cherokee suspension. And that is exactly the point. It is extremely easy to lift an XJ 7" without introducing any significant geometry issues, but extremely difficult to do the same with a Jeep quad coil suspension without fundamental re-work. That is purely for one reason: the XJ has rear leafs instead of coils.
Now nobody would build this design for a buggy, or a pure offroad bias design, but to have excellent stability and load bearing on a big lift without needing overly high spring rates could be an excellent design goal because you are eliminating the issues introduced in suspension geometry by running a highly angled link system at the same time (and using the simplest possible suspension technology in the process). The 80 and the XJ both share a very balanced front to rear weight ratio, so it seems like a very viable application to me.
This is what an XJ on this exact setup (7: lift) looks like on a 12" travel shock on 37's. This rig has run the Hammers and other BOTW trails and it is not a trailer queen. Notice in the road shot the mount position of the lower arms - when the tire clears so does the arm, but because it is mounted flush to the axle (LCA) the angles are still good from a geometry perspective despite not running a typical 30+ arm length in suspension conversions.
I wish I had a pure project 80 to try this conversion - of course at that point I'd have enough lift for 39's and you know where all of that is headed
: 
