My point about the alternator that you ordered is that that one COMES WITH A BUILT IN REGULATOR...
I'm helping another member with his 69 Dart and he made that same mistake. I told him to get the proper field, amp rate, pulley config and somehow they sent him that one with the internal regulator which requires bypassing whichever factory regulator that you may have right now. They do offer the same alternator WITHOUT the internal regulator which will just bolt in and clip up to your existing wiring without any modifications. You just have to make sure that they know you want the one without the internal regulator.