Slant 6 Block Crack

What do you think of this? Fixable? Ignore? Future Coffee Table? I *was* planning a full rebuild with upgrades, head porting, higher compression for this engine. The head looks good. Actually, the cylinders look really good. But this crack?! Ugh. Is this common? Why would the block crack at the alternator bracket stud?

1974Aspen225_cracked_block.jpg