Trying to figure out if I have two oil leaks or an oil and transmission leak on my 73 Duster 318

413 said
Castrol super clean and a pressure washer. Then you can see what up. Either from top, or oil pan or rear main.

Your drain plug is a lug nut and a bolt. And it’s most likely leaking through the bolt threads. It looks like 1/2”x20. Hold the bolt head and loosen the lug nut, then unscrew the bolt. It’s the old backyard fix.

I believe this is what he has........I installed lots of them when I worked in a lube shop back in the 80's. Never heard of the lug nut fix....But I've been wrong before :)