Large RPM and Vacuum drop when shifting from park to gear

At first glance, your torque converter could be too 'low stall'. What converter is it?

Or, you could have vacuum leaks. Or...a bunch of other stuff.

How much timing are you running? I'd set if for around 20 degree initial, with the vac advance in operation. and 32-34 degrees total. Ignition advance idle does wonders for idle quality/strength (and you'll see it in good vacuum-at-idle readings).