The way to tell if your bars are not big enough is if you can't adjust them enough to take out all the rise you want to take out of the front of the truck, then go up a size.
As others mentioned, learn all about your hitch and how to set it up yourself. All you need is a level parking spot, a tape measure and some masking tape to mark 4 spots at the truck corners for measuring. Personally, I take out all the rise in the front and even a little more if I can. Experiment and see what works best for you. You can weigh things later to prove to yourself how you did, but weights aren't necessary to set up the hitch. They are nice, especially with a smaller truck, to make sure you aren't overloading the truck or an axle (likely a non-issue with yours).