That head is very repairable. Since the crack isn't exposed to combustion heat and/or compression pressure, all the repair has to seal is cooling system pressure. That's probably 7 PSI or less. I'd suggest a good cleanup, wire brushing, bead blasting, etc. and follow up with a little air pressure and bubble soap to find both ends of the crack. Then stop-drill the ends to prevent any further spreading of the crack, and "sew" the area in between with overlapping tapered-thread cast iron plugs. The plugs and the tapered threading tap to install them are available on Ebay.
Jerry
