MP also used to make a rear main bearing that was supposed to help reduce the chance of the seal leaking. It had to grooves cut in the lower half to direct oil away from the seal. (I don't know the part # off hand). I just had this issue with my 408. I had the black seal as in the picture above and it leaked for no apparent reason. I replaced it with the orange style one as in the picture earlier in this thread and duplicated the rear main bearing like the MP unit and it solved the problem.