Jeremy,
I built a truck vault to go in the bed of my truck with a cap covering the bed, (this way I have a seat left for my dates). [big grin] It holds a lot of systainers and tools, has some benefits and drawbacks but overall am satisfied with it so far. I'll take and post some pics if you're interested in going that route, I built it like one I saw here on the fog a long time ago but never could find it again so went from memory.
Honestly, there's never going to be enough room in a truck for you, especially when it's not even full size. A van is the way to go if you get any bigger, or a trailer pulled by the truck. Just my opinion.
CB