I have some radio equipment from my old Land Rover "expeditionary" vehicle, but it has sat in my garage since its older tech. I think as far as stuff that would be permanently mounted on the truck radios and GPS are good places to start. I know the trucks are outfitted with GPS already but a solid Lowrance system would probably be a great backup. I have a Leitner Designs rack and I have mounts for some rotopax, so extra fuel is on board. Everyone wants look tacticool like they are on a SEAL team or some shit, when in reality, after a certain point its just really expensive LARPing.
Reminds me of a youtube video I recently watched were a guy got a 30 some odd foot boat and said that he didn't need radar and that the one on his boat was on older type that "didn't work" because the "radar stations are on a newer frequency". Nevermind the boat next to him as the exact same model of radar.
As far as what I would use, I've always romanticized using a sailboat. Doesn't work too well on land, but as long as you know what you're doing, you'll be fine. Lots of them have solar panels and water makers on board so you'd be set for the essentials. As long as you had canned goods or dry food you should be set for an extended haul.... that or a submarine lol!
Forgot about the SCABs and their dinky tanks. Better have some jerry cans ready to go!