headers vs manifolds on a 318 2bbl difference ????

My small cam, stock 340 dart is designed to run WOT from idle up and torque up to 3500 is most important.
WOT from idle or low speed when safe, breaks the tires loose easily but you can't push it on the street to 5500 rpm. And there are straight stretches coming and going from all of our cruz nites were you could run WOT if there is no traffic but even if you stay in it to 90 mph it would only be 3700 rpm. There is no place anybody could run to 5500 rpm on the street safely.