Ignition on GMs should have a manifold vacuum source, not ported vacuum, so you're looking for the 20 inch vacuum port. The timing should be set to spec (I think 6 deg BTDC) WITHOUT the vacuum hooked up, but plug the hose so you don't have an abnormal vacuum leak. When you hook up the vacuum it should return to smooth running.
When its running fast like you said, does it just sound like fast (cold) idle or does it sound like an abnormal condition? If the distributor setting and vacuum change doesn't help, I would try backing down on the idle setting to see if its off, but it didn't do that before did it? Remember how many turns you set the idle screw (and make sure the choke is fully off) so you can go back to where you were if necessary. If you're pulling 20 inches of vacuum you can probably set idle to about 500-600 in gear and 750-850 in neutral.
Good luck