Vacuum advance with the 273 Power Pack looks like 23*, and comes in from 6 - 12" Hg, so that definately would be used with ported source.
Could be a little much for today's fuel if the mechanical comes in fast.
Mopar Perfomance recommends 50* while cruising steady on the highway. So if the mechanical timing is around 30* at 3000 rpm, then really only need 20* from the vacuum advance to get the 50*
I'd start with a vacuum unit with 10 to 12 distributor degrees in the arm. Then adjust when it comes in depending on the mechanical and what the engine seems to like.