it is possible that the holes were not drilled deep enough to go through the casting or that the casting was extra thick on you heads so they do not go through , while Mopar did an amazing job designing the big block in the mid -late 50s the engine has some issiues , having the holes go into the water jacket has always been an issue for me but it may have to do with casting technology in the 50s , at least the head bolts do not go into the water jacket causing coolant to leak into the oil up the head bolts like all the chev engines do