With the luggage for my wife and myself for a two week road tip, space is a premium. No tool boxes.
This is what came out of my car when we arrived at the hotel. And it all has to go back in. And that does not include the tool bag, or my helmet bag.
I have one fairly small bag with the tools I might need. I may just go to the store and buy some of the things I put in there, and just keep them in that bag and keep it in the car.
When I drove out to Palm Springs, CA (4th trip to CA) it was only 107 or so every day. The heat in my car was 135+ and my rear view mirror just fell off and was on the dash. I had to go buy a scraper, rear view mirror adhesive, and a set of Allen wrenches to get the mirror off of the puck that glues on the glass. Scrape everything clean, and new glue, and it is still in place.
I will just make up my one road kit for the 911. My El Camino has a large storage area behind the seat. No issue with hauling some tools.