Did you note Skids72 comment about setting the timing with the vacuum advance disconnected?

If you don't you'll end up with retarded timing.

With the cam you have and assuming the timing is retarded 11" vacuum is about right.

If . . . the engine is idling at 600 rpm or so and you increase rpm to about 1500 the vacuum gauge will indicate 17"-19" of vacuum.

I'm asuming your vacuum gauge is connected to full time manifold vacuum.
If it's connected to ported vacuum you'll get readings that are not correct.