Rb headers

I have a '67 Dart w/6. I also have a 440 to replace it. The engine build should get about 400-475HP. I've seen some real plumbing nightmares with headers in these Darts. What's the best header or factory exhaust manifold for this combo. This car will see many street miles and about 10 days at the track each year. The tranny, converter , rear and suspension will reflect goals of 11.50-12.00 in the 1/4. Thanks