Slant six exhaust manifold for 64 Dart
Try a company called Silverseal at 734-479-2255.
When we put my ex's 64 Dart back together I got one from them shipped to my front door for under $200 and it had a bunch of hardware with it. They sell them brand new.
All the old ones I bought had the "typical" crack in the runner. It's best to buy a new one.