I have a similar setup in a motorhome. If you use the inverter to power only 240 volt equipment, there is no need for an autotransformer on the output side. You would just connect the two hot leads and the ground to the appliances, obviously through the appropriate circuit breakers or panel, etc. 240 volt does not use a neutral. However, if you want to power 120 volt equipment an autotransformer is required, I would recommend a 100 amp unit. This article may help. One thing you may want to consider. I carry an additional 32 amp autotransformer in case I have to connect to 120 volt shore power. As the inverter only inputs 240 volts, the autotransformer converts the 120 volts to 240. The maximum 120 volt shore power is 30 amps (at least for campsites) a 32 amp autotransformer works fine. As mentioned above, for the shore power input you only input the two hot leads and ground. The neutral is not used. Again, I might consider the post to use only one inverter and run everything through one electrical panel.
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