Which leaf springs to use?

Not easy to modify the rear segment as the
metal is hard as Hell.
But you could easily modify the rear spring hanger
to move them up .75.
Male sure shackles are leaning BACK and not forward
when you are done
Plus be prepared to reroll you front fender if the tires are large
diameter.
I routinely move up the rear end .75 forward.
Sometimes the K member as well.