Can I ask an A-body question on here?

[JS29]

Exactly. Cars with longer shackles will have a reverse arch on the back half of the spring generally.

Dam physics   

[Marksmopar1]

 I had my springs re-ached for $175 and that included new bushings. CND funds as well...
I wouldnt extend the shackles... not the way to go as it effects vehicle handling and looks like crap.

If you get a god deal on new springs ..go for it. As for me, I always look into re-arching my originals... just me.

[Jocigar]

Ok, she's mine

Here are pics... not sitting level  hopefully all part of leaf spring issue.

[Chryco Psycho]

The back 1/2 of the spring is the soft part giving ride quality , longer shackles only push the spring down lowering the front spring eye will help more or just re-arcing or changing springs is the way to go