I think we have general consensus here that the OP should use at least 4/0.
The original question was about the automotive ampacity tables being different and confusing.
I prefer hard math numbers like I posted above, or actual test experiences like @scrubjaysnest
It might be better to use actual electrical code tables.
I wont even pretend to know USA codes but I know they will be close to Canadian codes.
We should try to keep our voltage drop around 3% - maybe 5% max.
But 5% at 120 volt is only about 6 volts, but 6 volts on a 12 volt system thats intolerable....
There are also de-rating factors to consider for the cable based on types of cable and application even duty cycle,,,
Since I an not an American, do not live in the USA, and do not use the NEC, or have even ever seen it I don't even pretend to know what the rules are for what we call extra low voltage wiring up here...
But I am pretty sure your Insurance company will expect you to follow these rules or they will decline your claim in case of a fire.
What I do for a living is a little different from homes.
My work is governed by codes related to heavy industry, high voltage and not general purpose wiring for homes.
I except no liability and claim no expertise in USA building codes and suggest you not listen to anything I say but instead refer all questions to Qualified electrical safety authority and the NEC and building regulation in your local municipality...
But that all said no one ever got in trouble for running a bigger wire.
Just know when to quit, if your pulling 500 your went to far lol
( if you go past the Dolphin people you went too far... )