This is a view of the temporary block on my T&C. The T&C has one big grill, while the Caravan had the grill sectioned, which I think you probably have with your Ram.
I just taped some paper over the grill and traced the outline of the edge with a sharpie, cut that out, and used it for a template on the cardboard that I'm using for the block. Then I just poked some holes in it, and looped some zipties through the grill and cardboard to attach it. I did paint it so it didn't stick out like a sore thumb, but I didn't trim the ends from the zipties, so you can see them in the photo. I will make a more permanent/removable block, but this was mainly to see how it would affect my engine temps. It's a little warmer, but not dangerously so. But I know that when I want to carry a heavy load, I will want it removable.
Good luck.