Say your running a carbed 350. What is your preferred source of vacuum to the vacuum advance canister on the distrib? Ported? Full manifold? and why?

I have run both of them on my car and seem to have better luck with the ported. As far a driveability, economy, and acceleration goes.

 

I've always hooked it up to manifold vacuum... cleans up the idle, doesn't smell as bad, runs smoother, sounds better, doesn't heat up as fast, and can run a bit less initial timing so its not as hard on the starter. I haven't found a downside to doing this yet.

 

the downside i have has is that when i have manifold vac hooked up my car operates at a higher rpm while cruising. I was told on another forum(CHP) that manifold vac is the way to go. So i tried it and the car stumbled and wouldnt accelerate normally, but when it did it cruised at 70 @ 2750rpms. It has an adjustable vac canister and ive used the heavyest springs in the advance. The car has a 700r with 2.73 rear gears. With it ported it cruises at 2000 rpms. With overdrive operating both times.
Any ideas as to why this is?