Rotor phasing is absolutely an issue, and with the poor and expensive availability of parts for those old girls, it might be tough, and you'd have to cut up a cap in order to resolve it. If you are enough of a craftsman to make the new mount variable (to change the trigger timing) it could be done. I would not. Before I did Pertronix (because of their proprietary rotor/ trigger wheel) I would machine someone's reluctor whether Ford, Mopar or HEI, and adapt it to a magnetic trigger or even Hall effect. And with that you could run a choice of some different modules
What you need, is a way to "justify" the rotor position at the point of trigger. If you don't want to cut up caps, If you were able to construct a test gap that accurately reflects a tower position on the cap "exactly" you could also do it that way.