Bob, I think you must be right. During the normal tape and mud process for sheet rock the gaps between the boxes and the sheet rock get filled with mud (spackle). In my case, with the plywood I didn't do taping, though I did use caulk and non-shrink spackle in a somewhat similar process. I didn't realize that I needed to fill the gaps around the boxes until I started to put the covers on and noticed the gaps. I had caulked around the bozes, but didn't fill them to flush with the spackle. At any rate, I have done so now, so all visible gaps are gone.
I think you are also right about the outlet ears, but in my case they never reached the plywood. Had I pulled the wires and then done the spackle, they would have reached the spackle, but I put the outlets in before I did the caulk and spackle process. As usual, I cost myself time and effort, but I got it done.
As for the outlet spacers, I have seen them as well. I couldn't find them when I was looking this last time, so I just made my own out of wood. In most cases I didn't need them anyway, except for a couple of boxes where I screwed up and mounted the box way too deep.
As of yesterday, all outlet and box covers are installed, even the ones in the ceiling that enclose the antenna amplifiers. I also installed the crank and pointing handles for the two antennas.
I also did some finish painting around the doors and finally installed the peep hole. I set it as low in the door as felt comfortable, but I probably should have set it even lower. Even with the wide angle of view I will only just be able to see the head of someone standing a reasonable distance outside the door. The inside of the truck is just so much higher than ground level, it makes for quite a compromise on the placement of the peep hole and the door handle.