Dreaded 460 Exhaust Manifold Leak

Here's the story on exhaust manifolds. We didn't have warping manifolds(or brake rotors) back in the 60's and 70's. The reason we have problems now, is that to save money, the manufacturers eliminated the nickle content from the metal, which really gave it it's strength. With the heat they stretch, warp, and break the bolts, most commonly the back right. The best permanent cure is headers. I went with Banks. Did the job myself. Yea it was a hard job, but your problems will be over for good. When you plane the manifold, it removes metal, and the manifold just runs that much hotter and warps again. Here's how you test a warped manifold. Take the manifold and put it on a perfectly level surface. Usually a supported piece of glass will work fine. Take a feeler gauge and measure the gap(warpage) all around the whole thing. If the gap is any larger than .01 inche, no gasket will seal it correctly, then you can try and plane it. But having been there done that, the Banks with it's 5/8 thick stainless flange is the best. Thorleys are good also, but never put cheap headers that have a flange less than 3/8. I wouldn't even do that myself. If you go with the Banks, save some money and skip the Ram Air part. It does nothing but make you feel good. If you have to drill out a broken bolt, they sell drill guides that keep it straight. However, you need to use a drill stop, because if you go too deep you get into the water jacket which is only 3/8 thick. Particularly on the back right. There are multiple threads on this issue if you search it. Good luck with it.