Assuming it is too late to drill and tap the block in the same location as a 109 block, then weld a fitting to front of the oil pan just below the rail, and set off a little to the pass side.
you can probably plumb some A-N fittings from turbo to engine block. My block has a 1/2 pipe thread hole in the back that i have no clue what it's for. I believe one of the A-N fitting companies makes a adapter that bolts up to the oil return on the turbo then you just have to make up your steel braided line. You may of given me an idea for my next project. I will post pix if i get it done.
I am working on this set-up myself, my turbo out for repair so I can only post pictures of the line mocked up. I am still playing with it trying to get the correct angle, I borrowed some more fittings from a friend to help me see which angle is best. I will post more picture when it is complete with the turbo
I attached a -10AN fitting to the highest part of the oil pan just in front of the starter.