Dave,
I have a 1954 235 truck (Hydra-Matic) engine with a crack like that. I assume it is a result of no anti-freeze in a cold winter?
I have a 261 that had a 1-inch crack in the block (2/3 of the way up the manifold side). I drilled deep dimples at each end of the crack, then cut a deep v-groove along the crack; then cleaned and roughed and cleaned the metal around the crack, and then applied JB Weld - about 13 years ago. No leak since then.
I would not buy an engine with a crack, but I'd try to save one that I know runs well.
