Just put in a fast curve as Dad had told me to forever; that is how they did it. I talked to a friend with a healthy 440 in his gasser Dart. He runs his locked out at 36° and 20° start retard in his MSD Digital 6 box. Thinking about manifold vacuum for advance there is high advance (adds 16°) at idle, then tapers off while the mechanical advance is adding timing. That is essentially full advance all the time except during crank/start. Mech is just replacing vacuum adv. Ported is adding at cruise and should taper off at WOT and be only Mech.