Factory distributor springs usually consist of one fairly light spring and one heavy spring with a slot that pretty much acts as a stop until the higher RPM. Unless your distributor has been worked on you should put in two light springs and then restrict the slots as needed to achieve the "mechanical" advance of all in at 2500-3000. Then check it at cruise RPM with the vacuum connected to see what your "total" timing is. I will let the conflict over wording settle itself....
