I am somewhat minimalist. As a rule of thumb, I only put in what I'd need for roadside. Unless I'm on a road trip, I'm always going to be nearby a cell tower or someone with a ham radio. I bring what I need for a day trip so I can to get back home, to a hospital bed, or to a hotel by the end of the day. My other rule is to only put things in the truck (or any vehicle, really) that I don't mind being stolen. The biggest example would be a truck gun. The only firearm I have in the truck is the one on my person. The last thing I want is for a thief to run off with a gun. I've actually had a lowlife ransack my Excursion before. That guy got away with nothing because he couldn't find anything pawnable in the truck. He totally missed where I hid the tool bag. Maybe I could've hid a gun there too. Haha.
On that note, this is what I usually have:
Recovery gear
Cargo tie downs
Hitch receiver
Napkins
Plastic flatware
Spare masks for the stupid virus
First aid kit (Trauma and ouch pouch)
Hand cuffs
High visibility vest
Essentials tool bag (metric sockets, crescent wrench, screwdrivers, allen/torx keys, wire cutters, multimeter, etc)
Biden T-Shirt
At some point I'll have an OBA as well. That's pretty high on my wish list.