89 tioga arrow ford exhaust leak

I was able to get all the bolts out of both sides on a 460. The original manifolds had warped and the gaskets had rusted through. An auto machine shop was able to re-surface using a machine called "belt sander" that actually does a precision job. On driver side, I was able to wrench them loose with a flex ratchet, all eight. Reassembled with new stamped steel gaskets, anti-seize compound both sides, and new bolts. Did passenger side a few years later and found the bolt heads were rusted enough to be no longer 9/16. I found I could mount a 13mm socket on a long extension that fit in the space between frame and fender liner. Pounded them onto the bolt heads. I found all 8 came out easily. I think it was due to the pounding to get the socket jammed on. Again, re-surfaced. Re-attached original crossover pipe and connected to a new Flowmaster 3" cat-back exhaust. I ran it another several years and no further problems. I'd made up my mind, though, that if a manifold broke, I'd install headers.