I've mentioned this before, but I will mention it again because it happened to me and I didn't realize it at the time.
There are some flywheel alignment pins on the back of the flange of the crank shaft. If those pins are missing, even one, you will be putting oil right out the back of the engine and it will look exactly like a rear main seal leak. Those holes go through the flange into the engine cavity. I have seen some people cut off bolts to use them to make pins. They will generally leak because they are too loose. Pins need to be used and pressed or driven in. They need to be tight to prevent the oil from coming through.
Of course, there is that other thing - the valve cover not being tight enough and letting oil run down the back of the engine.
Just a couple of thoughts!
