I would honestly have thought that it would have burst a pipe before splitting the rad like that, any chance you can post pics up of the splits in rad, may just be some sort of fatigue, or old damage to rad, hard to give a solid opinion without seeing it all in the flesh, but I would be inclined to try another rad, and make sure you bleed the system properly, as it is sure to be full of air, you may even have to burp it, I had to burp my hawk when I put the engine back in as it was pinning the temp gauge into the red almost as soon as you went up the road, burped it and all wAs well