Advice Please On A Milodon Oil Pan

[Wedg2Go]

WOW! Just Wow. This oil pan is beating me up!    I know my 440 is a relatively "New Build" and it will take some time to set nut and bolts to torque specs after some break-in time. However, this oil pan is refusing to stay put. Yesterday, I discovered a plug had shook completely loose...Gone! This is where the oil temp sending unit goes - If I was using such an item.

I know I will need a 1/2" pipe thread plug. Bigger question is brass or steel and will I, or could I, have a need to seal the threads? This opens straight into the oil reservoir.   

[1 Wild R/T]

brass or steel, either is fine... use pipe sealant...