Newbei 67 Plymouth belvedere 318 2bb dist vac port is timed or full.

Not to disagree with Steve, or be disagreeable at all, but here is an interesting read for you:
Ported vs. Manifold Vacuum

Also, the instructions that came with your 1406 probably told you to use ported vacuum "if your engine is emissions controlled". Unless you have added a bunch of stuff to your '67 it is not emissions controlled.
The bottom line is that it may not make much difference in driving. Biggest difference is where you will set initial timing.
C