Here'* a suggestion. Unless you have a specific reason for messing with the badly placed plastic drain valve, leave it alone. Why? 'Cause with older cars, too often when you go to open the drain, the rubber seal inside tears or twists and you can't get the dang thing to seal up again without pulling out the radiator and repairing it. Drain the rad for top end jobs (like thermostat) by using a piece of smaller diameter rubber or vinyl hose to siphon nearly to the bottom of the rad side tank. You can put the hose in a gallon jug and save the coolant for re-use that way. If the rad needs to be completely emptied, just undo the clamp on the lower hose on the passenger side and drain it there.
Just my $0.02.