It's a shame you had to cut the headers off to get them out. THey are a pain, but perform well on the 390's.
There are a few companies that make headers for your car, but they are pricey. Hooker, JBA and FPA are 3 I know of.
Do you still have the cut up ones?
The exhaust manifolds are easier and cheaper to find, but make sure you get the correct ones.
Good luck in your search.