Thanks for the pics. With you ground shading, you really don't notice that it's just a flat piece of posterboard. One thing though: your dashed lines should be yellow.
Good luck with the company diorama. That looks HUGE!
One thing you might want to consider is that the truck is 1/25 while the sandbags are 1/35. They will probably look too small. Remember a standard military sandbag is 14" x 26" (in 1/35 that's 0.4" x 0.743"). If you use these bags they will be 10" x 18.5" in 1/25 scale. Food for thought.
These trucks could be rated up to 1-ton, but I'm not sure with the "rating" for the Texaco kit is.
Have fun with this kit. It does go together well, but as usual the tires are bad. One thing that I ran into with my build was the pins for the grill were too long, and hit the radiator causing the hood not to close properly.
The Czeh Truck Modell sets come with wipers to replace the 2x4s that come in the AMT kit. I used KFS P/E wipers on mu Astro & Titan, and it really does improve the look of the truck.