Yea I would I would think it would be pretty cheap and easy ti remove the cover and weld a pipe bung in it.
If you do weld a nut on your plug be sure to ground it close to your weld not where currant will travel through your bearings.

 

Could we get this post back on track.

So what brand and type (i.e. weight) of rear diff oil should we be using? My truck is below.

 

leave the plug alone.
drain via taking the cover off.
fill via the vent.
I fill this way anyhow so I can sit instead of lay