RPO-254 maybe?

https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1410998.html

There are added springs for extra loading that function all the time.
There are springs that do nothing until the weight on the rear is heavy enough to make contact.
There are low cost add-on non GM versions.
There are junkyard coil springs added (welded on) because the old leaf springs are sagging.
Old work trucks can see almost anything in their lifetime.

The stock 1/2 ton without spring options will have 8 leaf rear springs gm part number 3683317 (please verify).

Last edited by buoymaker; 04/03/2022 10:44 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."