Do the 318's have a rear main seal?

This my first classic car and I took it to mechanic cause I saw oil coming out between motor and transmission.I told them to replace the rear main seal. He told me that since was going to do the rear main seal he might as well do the oil pan gasket, so I agreed. When I picked up my 71 dart he told me that it does not have a rear main seal. So I have wondering if it's true. Sorry for the domb question.:-k