I wouldn't drill that with the chance some metal shavings might get in the crankcase, knock a hole in it with a sharp chisel and use the honkin big screw driver to lever it out ... and yes, it's called the road draft tube, no "valve" involved and no pressure possible in the pan if it's working correctly
someone might have removed it cuz they didn't like the truck spotting up their driveway, if there's not some air inlet and a non-stock hose into the air cleaner from somewhere to ventilate the interior, that'll be the reason you need to rebuild the engine
Bill
