Are you getting it cheap? Block prep can be expensive, figure you need mains aligned, decks cut, and bore all standard costs before you get into the cost of the crack repair. Sometimes these old blocks aren't worth it.
I'd bank on at least 1500 added to the cost to get it ready for crank and pistons, depending on cracks, could even be dead on arrival
Also, remember some are solid lifter only, not a show stopper, but changes the tune (and sometimes risk) of a build.