Yes, the LG referenced needs 240V AC so it won't work on your existing generator. For 120V you will probably need two outdoor units, one probably at 24,000 btu/hr that will service two indoor units and another 12-16,000 btu/hr unit for the third.
You can't put the outdoor unit in a storage compartment. It needs to be open to the air. Maybe mount them on an extended (and reinforced) bumper.
David
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