I always thought the "0" arms were 1.6:1 ratio, but then I joined the CRG. They are 1.5:1, long slot rockers for the higher lift cams. Shot peined ? Different metalurgy ? Not sure, might have to go dig in the CBTN for that.
I'm proud I resisted the urge to replace them in '75 when I rebuilt the Z. I did change the springs and retainers, but fortunately kept both and the lash caps.
Someone else can fill in more blanks, I'm reasonably certain -
Regards,
Steve