[maple_leaf_eh]

Look up Metal Stitching. There is a company that will sell you drills, taps, jigs and fixtures to repair castings and/or machinings. The machinist drills a hole along the crack, sets in the pin of the fixture, and alternatively drills and taps holes. He screws plugs into holes with threadlocker and proceeds. Eventually the crack is filled with plugs.

Don't know how well they'll work in your application, but if you are looking at large $$ for a replacement block, this might be an option.