I have eddy heads on my 408 in a 72 demon. The car had hooker comps on it and I kept them . The headers leak- not enough to backfire on decel but enough to tic some. The gaskets just barely fit if you pull up on them and maybe stretch the holes a smidge. I've used the fel-pros and last time I switched to the reusable multi layer aluminum ones ($). They still leak a little.

I have seen another member here weld up his TTI flange a little to get a good pinch on the gasket.

I am very interested in this topic. I am looking to get some new headers this year- maybe tti or dougs? I would like them to fit without welding and I also have power steering so that limits me even more.

I'd love it if somebody knew more than I about this but in the meantime I hope I helped.

Kevin