You should have drilled the top oil pan flange while the engine was out. Its soft pot metal but you need to catch the drill tailings. Then you can install a return line from the separator to allow the condensate to go back into the sump. Or find a oil pan off a donor engine that already has the opening.

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body. '87 300D w/ Sportline suspension. No more '79 300TD w/ 617.952 engine at 367,750, it was my annual driver to Texas and I sure don't miss it poor A/C heater system!