Rear oil pan leak, is it the rear main or pan

I have a 408 stroker with less that a 1000 miles. I have a leak at the rear of the pan. Is there any way to tell if it's a pan gasket leak, or rear main seal.
If the trans is removed along with the pan, is there any way to tell where the problem is? I don't want to change the pan gasket and just hope for the best.

Thanks