I've been researching this lately as I want to remove my 3" blocks from the back. And since I'm re-doing my suspension again I want to make sure I'm happy with it.
I found this website:
https://www.generalspringkc.com/Leaf_Springs_Chevrolet_GMC_Truck_2500_1973_1987_s/1829.htm
I was just going to do a shackle flip and be done with it- but I have 52" springs. Now I'm trying to figure out if it would be worth it for the 56" springs.
As per the website above I have 7 leaf 52" springs. 2,775 lb spring capacity.
I'm looking at the 9 leaf 56" springs with a 2,600 lb spring capacity.
In theory they should ride better and have more flex- but will they? A 40 year old spring gets soft- so are my old springs better to keep?
The new springs should provide some lift I'm thinking. Maybe 1-2" I'm guessing. Is that correct to assume?
With the shackle flip I've read the same as what the blind chicken said. Angle the hangers forward for 52", back for 56".
HOWEVER- I've seen different things online for what length shackle to buy. I wanted ORD's "normal" length ones that are 4.5". Some say that those are too short for the 56" springs and they won't be at the right angle. They then say you need the 6" shackle- but ONLY on a heavy vehicle. On a light vehicle the shackle can flip the wrong way.
Anybody have any input to shackle length? EDIT: I did find for a fact that ORD themselves do not recommend the 4" shackle flip with the 6" super shackles.
OP: didn't mean to hijack your thread. I just figured it was quite similar to your questions and maybe it would be good for you too...