Here's what I did (not the easy way, btw)
I also converted to 4wd by using the dodge dana 60 in the front. I went ahead and used the dodge coil springs as well since they made to carry the cummins anyways. This required a lot of cutting, thinking, cussing, and work. Leaf springs would be A LOT easier
For leaf springs, I think I would call a spring shop and get some input from them.