I hada similar issue( and yes it was my pan )

I ordered a brand new steel pan for B series dodge van with a 36RH trans. ( mid 80's models )
99.9% of the people will never catch it that it wasn't the original 1970 pan. It came in a black E-coat finish and I put it on with nothing but the gasket, never leaked again. Never even scuffed the e-coat up or used any kind of sealer.