> I would suggest a close examination of the fit between pan and the mounting
> plate.  One way is to stick a light bulb in the oil pan (remove oil first)
> and then put the pan on.  If you see any light around the seam then you may
> have a dented, ding or mussed up surface causing the leak.
>
> Ed

Ed,
The stock oil pans are stamped sheet metal and in no way straight. There is a need for gasket and some sealant to fill the imperfections. The bottom of the block  is not perfect either. Between the different housings there is some mismatch too.
Buly