DJ,
As you most likely know, there were no optional front springs on 3100 trucks, but there were optional heavy-duty rear springs. 8 leaves were standard and the option had 9 leaves. In both cases, the spring width was 1 3/4"
http://chevy.oldcarmanualproject.com/chevyresto/51128.htmSomeone added helper springs above the axle on your 3100 truck. Non-GM helper springs were readily available (J C Whitney was a well-known mail-order source).
What are the widths of your main (lower) springs, and what are the widths of the auxiliary (upper) springs?
