Dually towing a short travel trailer! You know what it is to be prepared for anything!
At least you could put in a 70 gallon auxiliary tank and not overload your truck.
Most refrigerators require a pure sine wave inverter. Most modified sine wave inverters are not well matched to a high torque requirement of your refrigerator.
The normal recommendation is to have the inverter located as close to the battery as possible (or practical). In my case, I wanted the inverter a little farther away, so #00 wire solved that problem.
Your dual alternators are great. However the 200++ amps that they can put out - only about 5 or 6 amps will fit through the stock wiring to the trailer. You can fix this with a Anderson Connector, such as a 50 amp forklift connector with some #4 wire connected to that, and to a 100 amp relay under the hood, with a 60 - 100 amp automatic reset circuit breaker feeding all that wire.
I connected my 130 amp alternator in my motorhome to the coach batteries via a 120 amp forklift relay with silver allow contacts, rated at 100,000 open/close relay life. Grainger part #6C017 about $30 when I bought mine a few years back.
Great work on your RV! I will probably do the same thing - with a pure sine wave Trace or Outback inverter when I get a new RV in a few years.
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SunElec.comFred.