headers or manifolds for 4 door 318 valiant

I had questions about install and durability on headers, too. I found a Dart Sport 360 where a guy taking the engine left the manifolds. The passages are a little larger than the 318s. I had to plug air injection ports on both manifolds to make them work in the Demon. This is a sort middle ground. The 340 exhaust manifolds are better still, but a bit pricey.