I seem to remember reading that the machining dimension for the oil seal diameter had been incorrectly quoted in some documents.
If this is the case and your crankshaft has been machined in this way there may not be a seal that will stop the leak.
Neil
My solution was to install cigar socket in the ash tray location (easy to put back)
I run positive earth so socket is fed and fused in an isolated negative earth.
Neil