[RichardJ]

>>my only vaccum port is from the carb to the dizzy. I hooked it up to a vacuum gauge and get 0 at idle. I can rev it some and get 15 <<

That is correct and it indicates that the carb is adjusted somewhere close to correctly. That vacuum port is called timed vacuum or ported vacuum. This vacuum is from a port above the throttle blades and should show little or no vacuum and will not advance the timing until you begin to open the throttle.

If you use manifold vacuum for the dist vacuum advance, it actually retards the timing above idle. It makes for a Band-Aid to solve off-idle pinging and isn't even close to the vacuum advance that Chevy designed.

Dwell must always be adjusted before the timing. Look for a used dwell meter at a garage sale or Craigslist and offer $20 no matter what the clown is asking for it. You are the only buyer he is going see, even if he hangs on to it for months.

Buy a new timing light, because they get beat up and you need one even with HEI.

Mechanics need tools, otherwise they're just cowboys.

>> only adjustment was to turn the mixture screw all the way in, then 2 turns out,<<

That's the bench adjustment, now you need to adjust the mixture to what your engine needs with the engine running.