I bought the built-in
30 amp and "converted" it to a portable. I bought 3' of 10/2wG romex and put a 30 amp twist lock plug and socket on it. I then cut it in half and installed the two halves on the EMS. Then I cut the wire from the shore cord/generator just before the breaker box, and installed a matching set of 30 amp twist lock plug and sockets. Then, I just plugged the EMS in and screwed it down.
If I ever have a problem with the unit, I can just unplug the unit, plug the original wiring back together, and I am good to go.