You'll need the new stud for sure. A package of exhaust studs can be had at any NAPA, Advance, Auto Zone, etc. If you're lucky, they'll come with brass nuts.
Probably need a new exhaust donut. Again, any auto parts store will have it--or be able to get it.
You can try replacing the stud with the manifold in-place, but you'll likely need to remove the manifold because the other studs will break when you try to remove the nuts, and the studs won't un-screw from the manifold without major heat (oxy-acetylene torch, or inductive heater.) Moderate chance you'll break one or more of the manifold-to-head bolts. Nope, this isn't a fun job most of the time. If the manifold comes off the head, you'll want to haul it to a machine shop to assure the cylinder-head mating surface of the manifold is still flat and smooth.
Put it together with brass or stainless-steel nuts on the new studs. Anti-seize the bolts into the cylinder head. Torque the bolts to 80% of spec, in the order shown in the service manual. I bet there's no gasket between the exhaust manifold and the cylinder head--and if that's the case, DON'T PUT A GASKET IN THERE WHEN YOU REASSEMBLE IT. The gasket acts like an insulator--the manifold runs hotter with a gasket, leading to warpage, cracks, etc.
This sort of thing has only been a problem for five or ten decades. I'm sure they'll come up with a "factory fix" soon. Until then, you'll be doing it the hard way, just like Grandpa did.
Or buy a brand-new Communist Chinese (or
even worse,
Vietnamese) exhaust manifold that STILL needs to be taken to the machine shop to get the cylinder-head mating surface planed flat and smooth.
Photos of a Dorman Chinese manifold--note rough surface, and cast-iron dingle-berry that would have disrupted exhaust flow if it hadn't been ground-out.
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[Edit] Sorry, my photos don't show how rough the machined surface is. In real life, it looks like the teeth of a single-cut file. Horrible.[/Edit]
