Seems like I have to keep advancing my timing

[CSHADES]

The timing chain is the most common cause of the timing changing like you are describing. That is why I said you should check the vacuum reading at a manifold vacuum port not a ported vacuum port. if the vacuum is dropping from16-18 inches that usually means the cam timing is changing. Ignition timing usually doesn't change much over the life of the engine but what you have going is interesting. I see it is supposed to be a new engine, what is the story on it?