Instant Center Changes With Leaf Springs?

[aotte1]

Thanks,
With the Cal Tracks on leaf springs, it will simulate a ladder bar rear set-up?

Any idea where the CG is on 1986 SB SS with World Products 400 SB ( alu head and intake) is, this leading me to ask how much you raise front rear spring and/or lower rear spring to adjust the IS ( instant center) . Do I also need different rear leaf springs?
Les