so this is another exhaust post. open headers have been talked about alot, but is it the same for an open exhaust manifold. my 67 289 has just the stock exhaust manifold on it right now without anything else. would replacing those with headers be a big difference in sound?

 

the only reason it might get a little louder is the thickness of metal as compared to the cast iron, but your mufflers will depend on the overall sound as well as engine specs.