Your truck has an alternator, they only produce 14v,
Your choices are a generator, or inverter
If you use inverter you still have too recharge the RV batteries, either with engine, or shore power
I have no idea how much power your Ford alternator produced at engine idle speed
It won't make much difference anyway, unless you install the inverter in the truck
The charge wires from truck to tt, are too small, so is the fuse in the charge circuit, the inverter in the tt will draw most of its power from the tt battery, it might even blow the trucks charge circuit fuse, going to the tt,
