Cracked block....recommendations?

Years ago a guy I worked with bought a cadillac cheap because of the same crack. The block had frozen and cracked from one freeze plug to the next. We flushed all the coolant out of the system, poured a bottle of barsleak in it and ran it. A wide stream of water slowly became several tiny leaks before completely stopped. He also put a weak system cap on it ( 7 lbs ). As far as I know it never leaked again.
I think the key to success with those type products is the flush. It isn't going to bond where antifeeze is.