Since the wiring systems on all the "M-series" military trucks are of the same numbering system and AWG size, (CUCV-types aside), I had a situation before the days of multi-volt LED's when I first paired an M818 with a civilian 48ft trailer loaded with numerous 12V lights.. (easily modified to series-parallel circuits).. The first time out at night with that modified setup I lost all lights a few miles from destination, fortunately on a very-remote secondary road with no traffic.. I was able to alternate between blackout drive and service drive to finish the haul.. The (automatic reset) circuit breaker would cool and allow a minute or two of normal lights before tripping out again. Sometimes longer, sometimes not.
It led me to believe the breaker had weakened during the trip and now couldn't handle the load but briefly because military trailers don't have as many lights as this box trailer did. The next day, I could not get it to trip while sitting in the yard.. A clamp-on ammeter showed acceptable draw, so I inspected the circuits and found a chafed wire under the cab in a tight spot where an intermittent short could occur. And that was the end of it. Hauled that trailer many years with both my M818's with no electrical issue since. A few years ago when i obtained a FLD-120, I swapped most all my trailers to multi-volt LED's so I could put anything up front without swapping lamp connections.
The moral of the story, you already have a beyond-adequate electrical system for what the truck is, and more.
Some people want 12V goodies in the cab and got themselves a converter.. I had one for a long time in a Cat 12F grader (24V) without any issue. It ran a 2-way radio, CB, and AM/FM/Cassette for days on end, even when shut down sitting in the garage with it on all day. The draw was minimal.
A cheap alternative (and I can already hear the groans out there) is to make a fused lead off one of the batteries to feed the 12V goodie, swap the feed to the other battery on occasion depending on how much you play it. We aren't gonna hear a radio good enough to enjoy while driving a deuce anyway. We should just want to listen to its own music
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