Yes, the DC-DC charger is wired into the left truck battery through a 90A circuit breaker. The 70A circuit breaker goes between the charger and the RV batteries. This is in accordance with the installation instructions for the charger.
If you already have 1/0 wiring feeding a winch on the back of your truck, you are 1/2 way there.
Be careful of the charger you use. Verify your alternator can handle it.
To help cool the alternator when parked and idling with the DC-DC charger running I used a regular 120vac fan plugged into the trucks receptacle. Truck has its own 480W inverter.