Idle Rpm High in Park, Low in Drive

advance the timing a little and see if it does anything. It may pick up idle RPMS. just dial it back with the idle screw. My 273-4 idled at 700 and dropped to about 690 in gear. Could not even tell it was in D. What AFR are you looking for at idle? 13's are about right. Turn the idle mixture screws for highest vacuum, then turn the idle down to get back to baseline and keep doing that until there is no more vacuum to be gained. Dont tune for AFR at idle. It is what it is.