Hi Rhgonzo,
Welcome to the Heartland Owners Forum. This is a great place to get your questions answered by friendly people who are willing to share their real life experiences.
You need to consider two types of loads: how much the truck can pull (towing capacity), and also how much vertical load it can carry (payload).
It's generally a good idea to match the towing capacity of the truck to the GVWR. The dry/empty weight spec is more a design number than an actual shipped empty weight. It doesn't include the weight of options, and probably doesn't include the weight of "forced options" that ship with every unit. It's not unusual for a large 5th wheel to come out of the factory weighing 1000 lbs more than the dry/empty spec. It's also pretty easy to add another 1000 lbs or more of your stuff. Add a little water at 8 lbs/gallon. Before you know it you can be bumping into the GVWR.
Same with payload issues. The spec for Pinbox weight is 2215 lbs. But you need to figure that loaded to GVWR, the actual weight will be 18-20% of the total. So You could see an actual load of 3,000 lbs on the rear axle. If your Chevy is a 3500, you may be able to handle that within your payload spec on the truck, which btw has to also include weight of passengers, pets, tools, hitch, bed liner, bed cover, etc. If you have a 2500, you'll be seriously overloaded.
I tow up and down I70 west of Denver a couple of time each year. My 2011 GMC 3500 handles our 16,150 lbs nicely. The engine/transmission/engine brake do most of the work going downhill and I rarely have to use the brakes. I would not want to try this with the truck out of balance from excess payload, or with more trailer weight than the truck is rated to pull. I find going downhill is much more interesting than going uphill.
You can get additional information on safe towing at
Fifth Wheel Safe Towing, a website started by another Heartland Owner. He's got lots of info and detail on how to figure this all out in detail.