Texas Jim here closing on this successful repair. Successful but not without the anxiety described above, drilling out the old studs. Because of the drill out, the "new" stud sockets weren't perfectly aligned perpendicular to the old sockets. After inserting the one stud, one was mal aligned a few degrees, enough that I couldn't just slide the manifold back on. So I ended up overboring the 3 manifold mount holes, up a 16th. Doing so created enough space to re-mount. I installed the new crush rings (from Myers) dry. The first trial run running the engine I had a fair amount of leak - but I torqued gently and while HOT, and eliminated visible leaks. I was nervous about over torquing, and breaking off the manifold ears with the holes... but no trouble. Telling an old timer friend, he advised I could have used a copper-infused sealant to coat the crush rings and prevent leaks? But so far so good.
OK one more thing - My exhaust pipe is a modern type, I do not have an exhaust collar. It was mounted with a crude packing held in place with a hose clamp. I think it was a 1 7/8 OD so it left a fair gap around the sides. So I bought an exhaust sealant product described for patching holes in mufflers, pipes etc. It goes on very wet/slimy, and hardens to a ceramic glaze. I sealed the pipe into the manifold, pushing it like you'd pack a wheel bearing. Its a winner - hardened and no hint of leak.
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