All hope is not lost. Modern welding equipment and techniques can repair that block. Check these companies. http://www.castmetalwelding.com/Automotive%20Repair.htm This company is in the UK, but they show a series of pictures that follow the repair process to give you an idea of what can be done. http://www.castironweldingrepairs.co.uk/welding_reconditioning_car_engines.html
Thanks for the link, but I think I can pick up a bare 289 block pretty cheap. I think I'll stick with that motor, it has all new connecting rods, pistons, lifters, valves, double roller timing set, good crank, oil pump, etc. So, I have almost a complete built engine, minus the most important thing.