This is a 2004 E350 Sportsmobile with a Dynatrac front diff. It has a bit over 300,000 miles on it. The spring packs are beginning to go from flat to negative arc. Talked to the foreman of a spring shop that specializes in truck suspension. He mentioned that the spring packs on the rear of my E350 are stock. Before I order a new set of rear leaf springs, I would like to know if Heber kept the stock spring packs on the rear diff and just added a 4" block for the lift.
I don't know about Heber, but that's what Quigley does. I believe U-Joint uses leaf springs from Alcan. If you want an upgrade a spring pack with no block is the way to go...might cost close to $1k though for the springs.
The distance between the spring hanger and the shackle should be stock so the new springs should be the stock length from center to center of the bushing. Then you can specify what you want for ride height with or without the blocks. I’d order a multi leaf progressive spring arched to eliminate the blocks that cause axle wrap.