At the very end of the crack drill and tap for a 1/8th inch short Allen set screw. You have to drill far enough to allow the tap to put threads in for the allen screw to go in. If you use a bottoming tap then you could likely avoid drill through.
The drilled hole will stop the crack from creeping.
Then take a Dremal tool or small die grinder and make a shallow V along the crack. Remove the Allen set screws and coat them with epoxy and replace it. Epoxy the crack or cast weld.
