There's a guy about 30 minutes away from me that had done one on his AD truck, but I'm having issues finding his name, number and address. I do remember his biggest bit of advice to me was not to cut the frame. He stressed that to me several times. And not to do the S-10 swap. Said it wasn't worth the time.
I found a 4 parallel link setup for
$589 before shipping and the cheapest leaves I've found have been right at
(model 2799 heavy duty) $530 shipped. There's a local spring shop here in OKC (formerly known as City Springs, is now Fleet Pride) that I am going to try and swing by this Saturday to see if they have anything that will help.
Anyhow, I'm working on a 52 3600 with a heavy rear end

I was able to get some others off of a 52 or 53 3/4 ton GMC. I put both on and am still bottoming out. The air shocks won't bring the rear end up at all when aired up and the frame weight put on them. If there are some other springs that will fit this old girl and give her booty a boost, I'd be willing to keep the springs.
I figure that with new(er) springs, the axle flip would work fine. And I really like the stance and height that the truck sits at, but both sets of springs I have currently don't have enough life left in them. Not surprising considering that they're 60 years old and have hauled so much weight during their service lives.