In a dream world, all headers are tuned. (to a point) As long as the tubes are close to being the same length. Stay away form the cheap brands like Flowtech and Cyclone (if they are even still in business) Hooker headers will make a large noticeable difference in performance. Heddman headers are very good too. The new collector design on the Heddmans will cut out the need to replace gaskets every month, too.
I had a '69 Chevelle with a wicked 350. I had Hooker headers, 3" pipe with no crossover and Flowmaster 40's. It sounded like pure evil. It didn't help that the car was triple black.
