Tom, that crack is so common that ford even had a number for it, its a crack into a bolt hole, you can have it welded and resurfaced if it makes you real nervous, you can see the same type of crack in blocks, ive run many with that problem and had good luck, if it really bothers you put in a block sealer, i use sodium silicate (water glass), if you use water glase FOLLOW DIRECTIONS TO THE LETTER, do not let radiator tubes become exposed to air with it in engine,, heat and air is what fixes the crack, drain and flush engine as stated in directions, do not drive car with it in engine, that stuff will seal a crack that you can put the edge of a knife blade in, if it were mine i would just run it but keep an eye on things, running hot or water in the oil