Shorty headers

Are there any shorty headers made that will fit a 1970 Duster with a 340, that will bolt up to stock exhaust? I currently have the hi-po manifolds, and a set of 2.5" TTI's.
Just looking for some added horsepower, if it's possible. I don't want to cut up the pipes, though. Thus why I'm asking for the shorties.

Thanks!