I have my front differential housing out and while it is out I am pondering adding a drain plug to the housing.

Here is my idea, drill a hole in the bottom of pumpkin, thread a 1/8 pipe thread, and add a recessed set screw for the drain plug. I would use a brass screw and recess it into the housing so it would not get damaged.
The housing seems thick enough and the screws come in very short lengths.