Hi @kellyfish, thanks for reaching out.
First off, I am SO EXCITED for your trip. There are a lot of factors to take into account, but I'm going to focus on the one that I wish I had addressed first when I took a similar trip years ago. Have you tested out and measured what will be the sleeping area of your Toyota? Find the ideal position and angle to sleep at, and you can gear up to those specifications. Sleeping on such a hard surface can uncomfortable, especially if you are a side sleeper. A firm, closed cell foam pad such as this Therm-a-rest or the Nemo Switchback should provide strong protection.
The best adventures start with a good night's sleep!