Thanks, folks. I appreciate the input.
The decals on the body are HO Railroad decals you can order to use on box cars . . . they are perfect in HO scale to be used on 1/24th cars. I am pretty sure if you have artistic inclinations you can draw them on there with ink pens, etc . . .
As with all decals, I always airbrush a little FUTURE CLEAR, let it dray, apply the decals smooth, and then seal them in with a bit of Dullcoat. Works very well.
To answer the question about the tarp. If you make the tarp over Saran wrap, the tarp should be able to come off the body after it dries rock hard. You turn the tarp over and either remove the plastic wrap alltogether or you can trim it off with a pair of scissors.