I can not see the count of leaves in the springs but looks like it may be shy a few setting ride height a bit lower and softer. count the leaves.
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0459.html

Also a stock set up on the 3100 for perches is much different, with the perches installed as in pictures you likely see about a inch drop in the rear from that setup.
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0456.html fig 86.

Last possible drop is in shackles, if the space between bolts and pin get smaller the ride goes lower.
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0454.html


Baking in the nice desert sun, breathing life back into a 48 3800 5 window.