[Volfandt]

30" of vacuum at idle? Whats your elevation. sea level or below?
Normal at my elevation (1000') runs between 17" and 22" at idle.

When setting an engine via the vacuum method I've had the best luck by 1st adjusting the idle to spec. 350's w/ auto's are spec'd to idle at 600-650 in drive. It'll raise a couple hundred rpm in park/neutral. Straight stick is 600-650 in neutral.

Then set your timing to max vacuum at the spec'd rpm then back it off approx 2" of vacuum. If your max vacuum is 30 then retard the timing to get 28" of vacuum.

Now adjust the fuel/air mixtures at idle to max vacuum. If the rpm raises turn it down via the idle speed setting. Don't be surprised if your vacuum drops some when you back the rpm down.
Remember you want to adjust the carb to max vacuum (-2") at spec'd idle rpm, (600-650 rpm in drive) not at 1000 rpm.

To get best lean idle, with your idle set to spec and timing at 2 inches below max vacuum, go back to you idle mixture screws and turn them in (clockwise), 1 at a time, inorder to just get a small drop in rpm (approx 20-40 rpm) or (a very small negative movement on the vacuum gauge, maybe 1/4"-1/2" per adjustment screw)

Theres alot of going back and forth using this setting method and alot of idling, make sure the exhaust is well ventilated.

Good luck
Dave