I haven't really looked that closely at my oil pan on my truck. But if this is manufactured similar to the oil pans that we used at Cat than some of the bungs were welded on the inside of the pan. A counterbore was chamfered around the hole where the bung was pushed through the hole. A BEVEL WELD of the appropriate size was placed radially around the hole. From the pictured of the failed component, I did not see any weld material around the failed bung. What I would be afraid of would be weld slag on the inside of the tank that could come lose or is already lose from the failed bung and damage the engine.
Another point everyone that is suggesting welding by a weld shop how is the welder going to weld this up? If the truck is similar to my truck, there is not enough room to work efficiently under the truck. Ok, you may say raise the truck on a lift! Most weld shops that I am aware of do not have lifts that would support an 8,000 LB truck. Where will the grounding clamp be placed? Most of the time it should be fairly close to your weld zone. Then an electricidal current is being pass through the engine. Will this cause any damage to the electrical components on the truck?
To me it is safer and less costly just to replace the pan and be done with it. If the OP does not want to buy or has one already an engine lift. They can be rented from a rental store fairly inexpensively.
Again, it is his truck and dime so, ultimately it is his decision.
GOOD LUCK
Let us know what the outcome is.