I'm pretty happy with my Hooker Super Competition headers on my 360, but my experience in working with big blocks and TTIs is that they are some of the best fitting units out there. I've also heard good things about Dougs, but no personal experience.
Recommendations on ones to avoid: Summit, Headman, Thorley, Jegs, Hooker Competition, Blackjack, basically any of the sets that wrap around the steering linkage.