Travis, I'm not kidding about the math component. That will tell you how much fuel you need, and fuel is the bulkiest component. If it's not much fuel, then it's small. If it's a bigger thing, then you're going to need a bigger vehicle.
My personal gut feel is that one rocket would fit in a trunk, but five kilos of warhead is just asking to get a few hundred kilos in return for minimal gain. Better to have a delivery truck rigged to barrage the boogers--you could store them in the firing position, open a hole in the roof, set a timer, run like hell.
Yeah, an IRA style homemade Katyusha launcher in the back of a truck or van, to saturate an area.