As others have said, you don't need it. Trust me!
The very early engines 32-34, had no crank case ventilation, and slinger rear main. Crank case windage pressurises the interior of the engine, which looks for a place to escape. Major escape route is through the labyrinth, so a return pipe was fitted, the open end of which is immersed in the oil in the pan. Therefore, that possible/probable/definite oil leak is eliminated [to a degree]
Beginning 1935, and all subsequent production, the crankcase has positive ventilation, therefore there is no pressurisation of crankcase, which precludes the blowing out of oil through the labyrinth, therefore, although the rear main cap was tapped for the fitting of the return pipe, the pipe was not fitted during production.
Certain 'dump truck' applications, whereby a heavy load could lift the front wheels off of the deck, could indeed, tilt the rear of the engine sufficiently to allow oil to leak out through the labyrinth, so in that application, the return pipe was fitted.
