John,
I don't have a Chev parts book at hand but the
MB-C1 Maintenance Manual lists the following for C-15A, C-30, C-60S, C-60L and C-GT:
Springs - No. of Leaves – Front: 10
Width of Leaves – Front: 2"
Spring Seat length – Front: 6-3/8"
Center to Center of Eyes – Front: 40"
Center of Front Eye to Seat – Front: 20"
HTH,
Hanno