My alternator wire melted.

Really hard to know how you wired it up.
Take one of those diagrams that I or Nacho drew and use them as a basis to draw what you did to your '71. Modify in MS Paint or print it and use colored pencils or whatever. Then look for the evidence of were it overheated and you can figure out what happened. And if its still not clear, you can post the drawing and photos.