My 422 smallblock build

I had this years ago on my tow truck with 351 clevland. I rebuilt the engine and cyl heads with new guides and all and when I put water in the engine water was gushing out from the back of one of the heads. after taking that head off and examining what was wrong it appears that when I put that head on it has got caught on the dowel pin during tightening and cracked a piece at the back bolt hole in the head. I had to find a new head and recondition it and install that one very carefully.