650 rpm for both manual and automatic 4bbl and manual 2 bbl. Automatic 2 bbl was 600 rpm.
550 rpm for all without CAP in 1967. (set with A/C on if so equiped)

The CAP setup traded a slight loss of power and efficiency at idle for much less CO and HC (but more NOx).
Higher idle speeds were needed so there would be enough power when put in gear, etc.