Turning /6 headers into heat exchangers, Just postulating Options

[Dr Evil]

A long time ago Root werks and I were going back and forth in a thread about ways to make /6 headers produce cabin heat. He had tried welding some tubing to the bottom of the headers, IIRC, and said that it worked fine until you got some air over it while driving (heat tapered off). I had an idea of tubes on each pipe that would be interconnected and would possibly tripple the heat output, but today I was thinking about it some more and came up with a better idea. I think that it would be pretty easy to have some fins welded up on the exhaust tubes along the stretch that will be boxed in on each pipe. This would increase the surface area without having to increase number of heat tubes welded to the exhaust pipes. With this idea you should be able to get pretty good heat and it shouldnt be a whole lot of work. Just fin it, box it, plumb it (cost less than $2500 or more for the HE and you still get the header performance).

Ideas?