When I did mine I cleaned the area on the oil pan with a DA and 80 grit about the size of my hand. Then I used a sharp punch (on Air Hammer) to puncture a hole in the pan like a bullet does, it tears the metal and no shaving go into the oil pan at all. Then I keep using a larger object to open the hole to the size I need it, and some help from a sharp chisel.
Then I weld washer on the end of the piece of tube I will be putting into the hole so it is slightly on an angle and there is about 1/2" sticking into the oil pan
then stick it in the hole and weld the outside of the washer to the oil pan.
I caution you make sure that you put the return in between two oil pan bolts so you still can remove the pan, and there is a baffel in there, if mine would have been 1 more pan bolt foward I would have missed it completly
See picture. It is not a good picture but it may help.