10 gauge factory wire was sufficient for most of TC charging on all my Fords.
I tried to run fridge on 12V one time and with >>110F outside, the fridge never cycled off, so after day of driving camper battery went low.
So I used propane for fridge, even I don't like the idea of open flame at gas stations, but huge convenience outweigh small risk.
Lance camper when I bought it - already had factory plug cut off and replaced with standard tow plug. I never looked forward to redo the wiring to Lance idea, but if you value safety high- do the truck wiring upgrade.
For long wire from truck battery to Lance outlet, I would consider #6 wire.
Also I found truck grounding on lousy side, so that could use upgrade as well.