I just spent some serious time welding them up this weekend. I have TRI-Ys and they had some back cracks at a couple of the welds. I think that patching them up with something else won't last as long as welding. check out J-B weld. I don't know if the stuff is good for high temps.
Also, I plan on bead blasting the headers, h-pipe, Y-adapters (so I can run open exhaust at racing events - hehehe), and adapter pipes and painting them with POR-20 (
www.por15.com).
Steve Leslie, 65 coupe in restoration. 302, toploader, A/C, disc brakes, bench seat