My advice-- if you want the chili to place well, in a work contest, you should do some kind of 5-bean "vegan chili" dish, or a green chile chicken "chili" dish. Real, actual Texas red doesn't ever seem to go over at company cook-offs.
However, if you still want to do a batch of Texas red, that's okay too. There's a lot of advice on this thread regarding how to rehydrate your chiles and utilize them for the base. If you want it to cook that fast then probably use just straight coarse-grind ground beef, 2 lbs would be a good amount since there's probably going to be a lot of other food there and people will just be sampling. For the chile blend, like jimmyjazz I like to use guajillo and ancho, and I also like to use some dried New Mexican chiles as well. Heavier on the guajillo and New Mexican, lighter on the ancho. For heat I'll use a handful of chile de arbol. Lots of bases for recipes on this thread if you look around.
I usually do not use tomatoes but occasionally I've roasted/charred a couple of quartered vine ripened tomatoes on a skillet and then blended that into the rehydrated chile slurry, and it gave some interesting flavor.