header question

I am considering putting a set of headers on my 69 swinger,I am about to install rebuilt motor with original 340 manifolds. As you know things are very tight under the hood, and my exhaust installer said they are a P#&@K because its so tight with the torsion bars etc.Would I notice much difference if I spent the money on headers and what kind are the best to use. Any info would be appreciated. Thanks Steve.