180amps?! WTH are you trying to do, charge a Tesla while you haul it cross country?!
I also very much hope that you already have the DC Power & Engineering 270amp alternator installed. Otherwise drawing that much power, even on surge, is going to kill your truck battery and/or the OEM alternator eventually. Even with the 270A you're going to need "the big three upgrade" AND a dedicated run to the trailer to handle that level of amperage. Obviously the 7-pin trailer connector isn't good enough as it's only fused at 30A.
@
Discovery
ran an 8AWG line with Anderson connectors to his trailer
seen in this thread.
How big of a cable you need for the 180A at 14v is really a question of length. I always try to use a
voltage drop calculator like this one. Just ensure you've got it set to DC 14v at the start, and to account for any vertical distance as well as horizontal. You can change the cable size and watch the voltage drop increase or decrease. Remember that LiPO usually require 13.5+v in order to charge properly, so you're not going to have much tolerance for that voltage drop. Having the LiPO near the tongue of the trailer will simplify your voltage problem by reducing the overall distance.