Visually, the springs on my WC56, WC53 and my in-restoration WC51 all look the same.
A quick look at the ORD 9, TM 9-808, 1 May 1945 shows:
CC-1090570 - Spring, front, assembly (WC-64 KD Ambulance)
CC-1088006 - Spring, front, assembly (except Ambulances)
CC-927754 -Spring, rear, assembly (12...