Park rpm vs drive rpm

[AmadeusCharger500]

Just did a rebuild on my 74 charger. The timing is set at 30@1000 It gets better vacuum at 36 but I thought that was getting a bit too far advanced. I know this timing is high but the vacuum goes way down when I set it to 15 btdc.

To get a fairly smooth idle I need it to be at least 600 rpm in gear. However the idle in park is about 1100 at that point and it seems too high, plus the car lurches when putting from park to in gear. Could this be caused by a vacuum leak or carburetor or timing?

Other than this and some throttle linkage issues the car runs and drives great.