[rotorwrench]

I've seen an unobtanium engine block heated up to dull red in order to do fusion welding on them. The old Duesenberg and Marmon engine blocks are well worth repairing if they crack.

The key is whether it was either warped or whether it has cracks from cool down. If it can be machined flat and round with little effort wherever it counts then it should be usable. I'd find a way to pressure test it first and go from there. Flatheads like to crack.