Neat project.
Another person did it in 1:48 scale. There’s some pretty good tips in there to help you on the way.
For people, I’d take a look at some of ScaleHumans people…you just have to be willing to modify them.
Give this guy a new hat, and he could be sitting on the running board.
There are other possibilities there as well, it just depends on how ambitious you want to be at modifying some existing figures.
Supply Line also has some other possibilities, plus they offer some other close scales.
Depending on your scale, I’d recommend Hubley vehicles for 1:20; you’ll probably have to get them from ebay.
There’s also some pretty neat diecast stuff in 1:24 that would serve as a starting point for that truck.