What does the back of your truck look like setup wise? Make a thin tool drawer that has enough room to shove a flat tool roll on if you want to take some bits away from the car if access is that important and then just a box for the bulky bits.
Failing that, tools are heavy and bulky and the only way to avoid that is to have less of them, for example not carrying a socket set but only the socket sizes that are on the car, and even then you can get away with spanners for a lot of those sizes as well. Probably telling you something you already know or do, but just in case.