I second what Paul said. Remove all freeze plugs and check for scaling and debris. Especially if you are going to remove the exhaust manifolds now. It will be almost like the engine is out on a stand! Well, not quite... Crosley's are well known for scaling and debris in the engines too, causing overheating. Also if you take the exhaust manifolds off and have someone weld a nut on that broken stud, then once it is cool, heats the exhaust manifold red where the stud is, it should turn right out. Heat is the key to stud remove on exhaust parts. May be cheaper than buying another set of manifolds. That is if your brother can't find his and donates his to the 'cause'.