I'd say that you'll have to use manifold vacuum if you run a vacuum advance. This may or may not be a problem you'll just have to try it and see. Sometimes when running a long duration camshaft the vacuum at idle can be quite erratic. The amount of vacuum will improve with more timing in the engine and drop with less. Sometimes this can cause the engine to idle well for a while and then suddenly become very erratic and then tend to either hunt up and down, die, or stumble. You'll just have to try it and see how your engine behaves. Being able to use a ported source eliminates these problems because it shuts off the vacuum advance when the throttle is closed.
I'd say give it a try if it's unruly disconnect the vacuum advance.
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