It may be that you have a burr or some type of groove on the end of your crankshaft. No matter how much you change the front seal it will still leak if thats the problem. There are only two solutions, pull the crank and have it machined or replace it. Neither are cheap nor fun to do. I would dread it but I would do it anyway. You might be able to pull the timing cover and look with a magnifying glass or strong reading glasses and check for metal imperfections on the end of the shaft. Then take some emery cloth, VERY fine and lightly sand it off and see if that works. If it is too deep to sand off then what I suggested may be the only thing to do. Either way its a pain in the posterior anatomy. I wish you well. Henry