I had originally put a 7-way trailer plug on the trailer when I first restored it years ago, but only ran the wiring for a 4-way light setup. I liked the way the 7-way plug connected to its socket, but only needed the 4-way wiring run back to trailer lights. Trailer just had stop, tail, turn lighting on it so just needed the 4-way wiring to run that. To get power to the battery box through the hitch plug for charging batteries while the trailer is towed, I needed to re-run the wiring with a full 7-way wiring harness.
I also added a water tank out of a 7-gallon portable camp jug I had. Ran some hose along underneath the trailer and added a spigot on the side of the trailer. Now I can get running water right from the side of the trailer.
Now just need some time to go use it.