Large RPM and Vacuum drop when shifting from park to gear
If you're stuck with 900 rpm idle speed for now, my suggestion then is just try to drop it a couple degrees more.
That would probably get the mechanical timing into the acceptable range. I say that assuming the distributor has an advance something close to what would be expected.
Just saw this. Generally a cam with more overlap will need more initial timing than factory emissions era.
They might have installed a distributor with a more appropriate curve to go with more initial timing.
Based on the two measurements you've posted so far, its not looking that way.
If that turns out to be the case, then that's something you'll want to address.
