I have seen new old stock for sale on Ebay. Sometimes good used ones. They do pop up from time to time. I would use cast iron headers from Stovebolt, or Fentons. That will stop the leak and help out with the mpgs and a bit more power. I would have it y'd into a 3" exhaust pipe. It will be quiet yet breathe very well. Just an idea. You can go to Kansas Kustoms and they take your old manifold am=md make a split header out of them with dual outlets. Its not real expensive but a neat way to go. Otherwise it will get worse. I hope this helps. Henry