Adjusting timng with Vacuum Advance

I have a stroked 360 408-412-416...... anyway, After alot of reading, I am seeing the definition of different timing refferances. Initial: being set at idle speed with plugged vacuum, Total: being set at 2500+ rpm's, and cintrifugal being the difference between the 2.

BUT, my question is, how can i be sure i am getting the most out of my Vacuum advance? when can i measure that and what am i looking for.

And, what does anyone think of the argument of using Ported vacuum as opposed to Manifold vacuum.......

Thanks!

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