Do a search on my user name to find a few other posts on headers. That said, I've had the same set of Thorley Tri-Y headers on my 304 for over 10 years w/o problems. I tighten the flange bolts 1x year or so and have never blown a collector gasket. They are not cheap and the one down side is that they hang down pretty far - as low as the spring hanger at the rear of the front spring.

I'd seriously look at the Edelbrock 'shorty' headers if I had it to do over.

Brian