I need some help with this. '68 J-Code, 302 4V. How do I repair the choke tubes at the exhaust manifold. My manifold is so rusted around that area that I can't tell how or even if that comes apart. Do I just drill the rusted parts out? I'd rather not replace the maniford. I've seen replacement tubes on the various Cougar and Mustang sites, so I know where to get the parts.