Adding 2nd air, converting from 30 amp to 50 amp

I'm actually on the verge of adding a third air to a 50 amp motorhome But I will wire it so that it can use internal or external power. I plan on having a corded end to the unit itself and then have two separate junctions with outlets, one tied into the extra circuit breaker on the motorhome panel and the other ready to be plugged into the Park pedestal if a spare 20amp outlet is available.