Vac advance will work fine on ported or manifold, but it needs to be set up and tuned specifically for the method used.

It won't work to just move the vacuum line and call it a day.

Personally I used manifold vacuum on my truck. From memory, I have ~14° initial, plus around 20 mechanical (reduced/limited from what stock allowed), plus another 15ish via vac advance. During cranking it sees the initial 14 and starts well, then goes to 30 something. At part throttle cruise, they all add up to ~50 something. At wot, the vac advance drops out to the ~34 total. Keep in mind most vac cans can be adjusted as to what vacuum they drop out at, which also makes a difference and also needs to be tuned.

Works great, and really cleaned up my idle.

I think stock called for ~5 degrees initial timing, then had an enormous amount of mechanical advance, which must be limited if you want to run more initial.