First, you should set timing with the vac advance disconnected, and the vacuum source plugged. Some guys mistakenly plug the vacuum canister not the vacuum source. This will be the initial timing you should use regardless of what vacuum source you use for the advance.
Second, I recommend you hook the vac advance to manifold, not ported. This will add advance at idle when your engine needs it, and produce a smoother more reliable idle.
You can run without vac advance, but combustion temps will be higher and your engine will be less efficient under light load driving situations.