Hello and thanks for taking the time to read this. I have 2017 F150 that I am using a battery maintainer on. At present, I have to open the hood and connect the extension cord every time I want to use it or disconnect it. l am considering installing a permanent 110V access port to make this task easier and not require opening the hood every time to attach or remove the cord. However, if I do that, I would like to make it as inconspicuous as possible. One place that appears to be appropriate and somewhat inconspicuous is using one of the two rectangular black box type structures below the grill on either side. I don't know what they are called, or what their function is. I also don't know if I can easily remove one, install the port and reinstall it, or if they are reasonably accessible such that I could install the port on in place and connect the wire to the battery maintainer. Please see the photo below. Thanks for any help or suggestions you might have.

 

I think the bumpers are universal and there is an open space behind the "filler" element you are refering to. In the past, Ford would leave the center space uncovered on EB trucks for intercooler air flow and if a license plate was required, they would replace the filler element with a license plate mount on one side or the other. You'll find that there are plastic push tabs on the back that hold that element in place. I don't think it would be that difficult to pry that element out while manipulating the tabs on the backside.

 

We call those breadboxes, they serve no use, and are held on by plastic tabs.

Im modifying mine to add amber marker lights to it.
You can buy them on Amazon for roughly 40$ cdn. The space is very limited behind the plastic, at least on my 2010

 

Be careful!
If your truck has adaptive cruise control, the Cruise Control Module (CCM) is located behind the driver's side "black box" That's the radar unit that monitors the distance to the vehicle in front of you and its alignment is critical.