The crack can be repaired. I have a 406 in my S-truck that had a similar crack. Because it was free and I have a complete machine shop. I bored out the head bolt hole. then threaded the resulting hole with 5/8" fine thread. Then installed a 5/8" fine thread bolt with the head cut off for a plug. Using an epoxy sealer around the threads. When it was set, I drilled the head bolt hole in the plug and threaded it. Then I drilled and tapped the adjacent water holes, plugged and redrilled the holes. Then decked the block. It has been in there for over a year. No problems.

I have used the lock n stitch on inner lifter valley cracks with great success!