How much is the head worth to you? Anything can be repaired for a price, in general unless its unique or impossible to replace I would say forget it...doing the repair properly is time consuming and expensive unless you do it yourself.
The technique for repair I have used successfully in the past is to construct an oven out of firebrick filled with charcoal, 12-20 bags is usually sufficient to get it hot and anneal it after the welding. Once the heads are good and hot (dull red) you weld the ground out crack with ductile cast iron SMAW rod and then peen extensively and recover the head with coals and seal up the oven with another layer of coals on top and a layer of firebrick to seal. Remove the head for machining once it cools which may take a couple of days. Its a good idea to keep the head in the oven as you weld and even have a rosebud torch to keep the weld area hot while you run the beads. Don't be surprised if the head cracks in other areas that you don't know about if you haven't had it magnafluxed first, I would consider having the head magnafluxed first before proceeding to ensure your not wasting your time with a no win situation.
I have a 100% success rate with this method, they don't crack after.
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”
— Han Solo