Ok now that I have wire size figured out I am trying to figure out the best way to set this system up, I have come up with the following and welcome any advice or critique.
I am tying into the aux alternator circuit with a 120amp busman circuit breaker, running 1/0 about 10' to the middle of the back seat where I will mount a waterproof electrical enclosure. The switching, battery separator and bus bars will be mounted in this enclosure.
The charge line in will go through a battery switch then through the battery separator to a bus bar, from the bus bar I will run through another battery switch to the bed plug for the truck camper. Also from the bus bar I will run to another battery switch that will connect to the in cab batteries. I plan to make the bus bar large enough to make the connections for the inverter as well as a battery charger.