Sir,
My dilemma was almost exactly the same as yours; a paid-for well-equipped truck (2006 with 40,000 miles!), but preparing to buy a larger RV. My fifth-wheel weighs within a few hundred pounds of yours and my RV garage is large enough for RV and truck, but not large enough for a dually.
After doing the research on my truck's running gear, sticker weights, and safe weights, I decided a tire upgrade was all I needed. I bought Vision Hauler 81 19.5 inch wheels from duallywheels4u and am very happy with this decision. The truck handles the RV very well with no stability problems whatever. It's actually more stable loaded than unloaded; these tires are designed to carry weight-and lots of it.
Without looking at your specific numbers, if your GM is like my Dodge, your axle is rated at something near 10,000 pounds. That leaves the tires as the weakest link, a legitimate safety concern.
Another poster (no names, no insult intended) suggested you would spend a lot of time or money to re-certify your weight capability. That's akin to re-certifying your toaster; nobody does it, nobody cares to do it, and nobody is overseeing that process (I'm LEO).
As for weighing your rig, a simple search will give you the answers to that question. It's easy but requires a little hassle of hooking, unhooking, etc.
Good luck with your decision.
Randy
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I have a 2011 Chevy 3500HD diesel, crew cab, long box, single rear wheel (SRW), 18,500 towing capabilities. I have seen conversion kits to convert my SRW to a dually, has anyone done this this? If so, are you happen with the results? I bought a 41 ft Heartland Big Horn 3750FL, 16K gvwr and I'm pushing the load capabilities for the SRW tires. I want to feel a little more secure with the camper load distribution on four dually tires vs. two. Any problems with this thinking?
Also, how can one weight the truck and camper to determine the pin weight? Thanks for your positive input and comments.