Thanks for helping me with these questions. Is there a cheaper alternative for the exhaust on 454's? I'm trying to put this project boat together and I think the headers are going to be to expensive this year. I have a wine taste on a cheap beer budget. lol

I don''t know how you think it would even be possible to use car headers on a boat.

If someone had the skill to weld and bend tubing very well and unlimited free time and materials they could build there own water jackets over a set of car headers but it would look like crap and they wouldn't last very long as the steel is very thin, I could think of better ways to spend my time but just saying.
I have seen BBC and BBF hooker boat headers , they were for jet boats/v-drives, water injected and come with a warning not to enclose them. I remember hearing in the day that there were no insurance company's that would insure jet boats and drives with "over the transom headers" as they were/are very dangerous to passengers , Smitty

What are they for?

Pretty sure "they" are no longer available as that was 11 years ago, Smitty