This Roco deuce and a half does not have the seats or the side rails. While not typical, these were sometimes removed, particularly if they were damaged or had to carry an oversized cargo. It is a good way to make use of damaged trucks. I got this one used with about eleventeen layers of paint on it. Including gold. There is always a gold layer.
The tow truck is a dollar store conversion. I got a dollar store tow truck and modified the rear end to make this Roco deuce and a half two truck. The US Army did operate tow trucks like this in WWII. The truck next to it carries a palletized cargo of a fighter plane engine nacelle and a fighter plane engine. US Army Air Corp.
Take a bit of sheet styrene and cut it to fit your Roco truck. I like to use Evergreen Plastic with the board pattern on it. It looks like a wooden deck. Lay it inside the truck bed and then stack various bits from the spares box. Almost anything will do, boxes, crates, oil drums, fuel cans, whatever is in there. I try and make them either totally generic, or work a theme. If I have some airplane parts, I used them for airfield trucks. If I have some fuel cans, and oil drums, they become a fuel transporter.