Eric ,
I have the later style C4 parts (1996). The lower arms measure 15 & 1/2. The C5 I have measure 17 & 1/2. The upper arms are 8 & 1/2 for the C4 and 9 & 1/2 for the C5. I believe Mike is correct on the measurement for the early C4 arms. I currently do not have any of those on hand to measure however.
Regards Brian