Chris, you need to slow down. Assuming you sell your TC you will have a fresh start. Don’t make the mistake that many of us do by buying a truck that is to small for your dream camper. I would first decide what model camper you and your wife would be happy with. Understanding how much it will weigh rigged exactly the way you want it is critical. Then pick your truck configuration based on your needs. Eventually you will probably want to tow something so tongue weight must be considered and added into your payload number. Unless your wanting a camper that is very small I think you will quickly learn that a 2500 will not do the job.
I don’t know your level of knowledge when it comes to trucks and campers so I will state the obvious. Understand how a truck is configured determines it’s payload. Buying a 3500 with a diesel,crew cab and 4×4 option will greatly reduce the payload. Gas powered,two wheel drive trucks will carry significantly more weight. Diesel trucks tow more weight. For 2020,GMC not only talks about payload they have addressed it. The same truck in 2020 will carry over 1000 lbs more than my 2016 and tow over 10000 more. To say I wish I would have waited is a gross understatement.
So lets talk briefly about TC’s. Slides are nice but they add weight and sometimes suffer from mechanical issue’s. They also cause leaks and allow heat to escape. There is a reason why Northstar has been successful for over 50 years. Refrigerators mounted on fixed walls normally cool better than one’s installed in a slide wall. TC’s with overhang will normally require a hitch modification. That means if you want to do it right removing your factory hitch and going with a twin receiver type that will allow the proper length extension to be used. My total set up installed was nearly 4K.
Hopefully, after reading this, you will slow down. The rig you are dreaming about will come at a very high price so choosing the right combination is critical. Go to a lot and look at the drivers side door jamb. The sticker there will tell you the payload number. Compare the difference between the trucks on the lot, or just carefully read GM’s print out for 2020. Your time to buy puts you in a very enviable spot, the new GMC’s are bigger and better than ever before. The opportunity to build a truly awesome rig is right there in front of you. I would diffidently custom order the truck once you determine how much truck you need. Good luck.