If you want to be atleast semi-realistic, A generator capable of powering something like a military faction would not fit in the back of a pickup truck.
It would have to be a tow behind trailer, and in all reality.. thats not really enough either. in the real world, a generator this powerful is so large that it has to be trucked in on a flatbet 18 wheeler and craned into position.
But since I doubt you'd go that far, the tow behind is the best choice.
Something like this
