Any ideas on this 340 block ?

Krooser said

I built my last early Hemi from a block that looked like that. One hour in the shot blast cabinet made it look new. Took a .030 overbore

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Yep. Shot blasting will make that block look new. I’d take a chance on it. I’ve seen way worse. My first 2 X blocks looked like they had been sitting outside for a decade and both turned out like brand new.