I need some help identifying the oil leak in my motor. It is a 1970 429 motor out of an LTD. I have an oil leak at the back of the motor that I thought may be a rear main seal.

I removed the oil pan and it seems like it is the pan gasket from what I can tell. I see no oil at the flex plate only at the pan gasket. (I'm assuming there would be oil on the flex plate if the seal was leaking)

Is there a way to determine which it is, the seal or the gasket?

Rear gasket:


No oil on the flex plate or in the bottom of the housing: