Pan gasket for 360. What one works best?

After looking at all the issues that could be causing a leak in the pan area, I got under the Duster to see if I could tell where the oil was leaking. The area between the pan and trans, on my 727 has a inspection opening that let you see the teeth on the front of the trans seems to be not where the oil is. When the moter was first done, the leak was being thrown back on my new TTI's, from the torque conveter spining. I put a piece of rubber over the opening, it helped to keep the oil off the headers. Inside the cover is wet from oil. I'm thinking rear main. Any thoughts?