Cylinder head has broken in a line about four inches long on the underside of the part of the head that the valve cover bolts onto. Can the head still be rebuilt or is it junk?
Your best bet is to take it to a machine shop and have them assess it. It's hard to tell if a head can be repaired just by looking. I'm sorry to say that my gut feeling is that it will need to be replaced but you may be lucky.
At the machine shop they can assess it using techniques such as pressure testing. It the crack is superficial then it may not be a problem and a simple skim may rejuvenate your head. It could also possibly be welded up so don't give up all hope and start searching for a replacement just yet.
The answer could depend on how rare the cylinder head is. If a replacement is available cheaply from a breakers yard, then why bother fixing it. If it is an extremely rare component, then I am sure someone will be able to fix it for a price, no matter how bad it is (within reason I suppose).