If you run return lines run them into the left side of the pan when possible..I do have the right front line ran in the the right front side of the pan. But the rear head lines run to the left where the most oil is coming out. You can see in this pic where my pan return fitting are even though I didn't have the lines connected yet. The right front pan fitting is also the oil level check hole. I also run restricted pushrods from smith bros. I drilled the heads to keep the minimum amount of oil in the heads. If you return from the valve cover you have to have an enormous amount of oil fill the head before it can get out the line..