I have posted pictures way back when of my old fiver with the second air installed but cant find them now.
I bought some #10 wire, a GE breaker box, a few 20 amp breakers and went to work. Using the front vent opening, I was able to fish the #10 wire over to a closet, (or bathroom), down through the closet ceiling, into the installed breaker box. Continued down into the roof of the roof of the basement then into some flex conduit over to the passenger side where I mounted a flush mount weather proof male plug on the exterior wall. When the second air was needed, I used a short #10 extension cord which supplied not only the A/C but another 120 volt outlet I wired to a different breaker allowing the wife to dry her hair while the microwave was on.