Replacing Captured Cords with After Market Cords?

I think the idea here is to eliminate any degradation of power which may be contributed by using the stock cord. If you put ANY device or modification before your stock cord,your stock cord will still degrade whatever is being fed to it. An add on is definetly not the way to go here. IMO

If you don't want to drill the box, just cut the cord, but leave enough room to work with, buy an IEC, install on cord, heat shrink it. Walla.

Make sure you identify which wires are hot and which neutral right after you make the cut.